I think the discussion is missing the mark. Science proceeds by constructing theories and these theories hold until a better one displaces them. It has been known for over 100 years that atmospheric CO2 absorbs heat. We have accurate measiurements that atmosphgeric CO2 is increasing and we know that release of old carbon from fossil fuels is contributing to this increase. Furthermore, we know from ice core records that past CO2 and CH4 levels have been positively associated with temperature. It is not unreasonable therefore to suggest that modern warming is caused by mankind. In the past, warming events were caused by external forcing such as solar activity, changes in the earth's orbit etc. However, to explain current warming by external forcing requires an explantion of why the stratosphere is cooling rather than warming as external forcing should lead to a warmer stratosphere. Consequently, there simply is not a better theory yet to replace the man-made greenhouse warming theory.

I would also like to say that measurements of environmental change are robust, particularly in the Arctic where change is particularly fast and measurements of multiple environmental factors overcome potential errors of instrument change when measuring just one (see for example Callaghan et al 2010 in Geophysical Research Letters).

Finally, I would like to defend IPCC. This is a rigorous process led by experts and the work is reviewed by experts. Rather than simply decry it as a political process, I would like to see examples of where data and interpretations are incorrect - if there are any.

So the bottom line is, to change our current understanding provide better evidence and better theories rather than simply criticise the established ones.

It is like egg or chicken, which one is the first? Environmental systems are complex, dynamic, spatially distributed, and highly non-linear. All things in the system are dependence on one another (interconnected). Do you remember Commoner’s principles that everything is connected to everything else, everything must go somewhere, and Nature knows best. So, whether anthropogenic or naturally it will link in mutual affection to the system (in this case climate change). Let say, people do legal/illegal logging or natural fire -->decreasing trees/carbon stock --> less CO2 absorption -->less free O2 and so on .... so we can't separately those actions because both of them will trigger climate change (naturally process). However, human activities accelerate the changes. That's all what I know, I hope it will help you.

Hi, I appreciate Hari 's opinion, I'm not an expert, but I think that things are complex and lead to confusion and controversies. It s Natural !. Nature is part of our wide environment, where a symbiotic relation exist between human beings and other organisms. Human activities could imbalance this relation, but i 'm wondering if human and nature are changing at the same rate ?

I would strongly say that the human activities influence more than the nature does. Eventhough the drastic effects of climate change has been known for decades, man-made activities which harms the environment is only on the rise and makes it imbalance.

In order to understand this we just need to know the history of earth's climate since it solidified from a molten mass. The nitrogen, hydrogen, oxygen and even the carbondioxide levels have changed and fluctuated. There have been periods of hot and cold climate. The deserts turned into forests and vis-a-vis. Human activities create an imbalance. Yet they are not of global magnitude, as a very large part of the earth is oceans, not inhabited by man. If the habitation in remaining 30% of earth is destabilising earth's climate then man must rethink about its role in this biosphere. Natural shifts occur in climate, human activities may disturb/perturb those oscillations in climate, but we are not yet so powerful as to change climate of the globe.

The following evidence is consistent with anthropogenic global warming. Separately, some can be consistent with other causes, but as a whole, they only match the fingerprint of human-enhanced greenhouse effect:

1) atmospheric CO2 is rising, and its isotope composition match fossil carbon. CO2/O2 ratio is also changing in a way that is consistent with our burning of fossil fuels:

- Manning, A.C., Keeling, R.F. (2006). Global oceanic and land biotic carbon

sinks from the Scripps atmospheric oxygen flask sampling network. .

58:95–116

http://www.esrl.noaa.gov/gmd/icdc7/proceedings/abstracts/keeling.rFF328Oral.pdf (only abstract)

2) LESS heat is escaping to space. In a warming world, this evidence excludes every cause but the enhanced greenhouse effect. In addition, the changes in frequency spectrum also point CO2 and CH4 as the causes of the change.

- Harries, J. E., et al (2001). Increases in greenhouse forcing inferred from

the outgoing longwave radiation spectra of the Earth in 1970 and 1997.

Nature, 410, 355 357.

http://www.nature.com/nature/journal/v410/n6826/abs/410355a0.html

3) MORE heat is returning back to the surface. This is the counterpart of the previous one, double-checking the greenhouse effect. Heat is trapped by the greenhouse gases, fails to escape to space and is "reflected" back to the surface.

- Evans W. F. J., Puckrin E. (2006), Measurements of the Radiative Surface

Forcing of Climate, P1.7, AMS 18th Conference on Climate Variability and

Change.

4) The vertical profile of ocean warming matches the way that would be expected in a greenhouse-caused warming.

- Barnett, T. P., Pierce, D. W., Achutarao, K. M., Gleckler, P. J., Santer, B. D.,

Gregory, J. M., and Washington, W. M. (2005), Penetration of HumanInduced Warming into the World's Oceans. Science, 309(5732):284-287

http://www.sciencemag.org/content/309/5732/284.short

5) Winter is warming faster than summer, nights are warming faster than days.

- Braganza, K., D. J. Karoly, A. C. Hirst, P. Stott, R. J. Stouffer, and S. F. B.

Tett (2004), Simple indices of global climate variability and change: Part II:

Attribution of climate change during the twentieth century, , 22,

823– 838, doi:10.007/s00382-004-0413-1

- Alexander, L. V., Zhang, X., Peterson, T. C., Caesar, J., Gleason, B., Tank,

A. M. G. K., Haylock, M., Collins, D., Trewin, B., Rahimzadeh, F., Tagipour,

A., Kumar, K. R., Revadekar, J., Griffiths, G., Vincent, L., Stephenson, D.

B., Burn, J., Aguilar, E., Brunet, M., Taylor, M., New, M., Zhai, P., Rusticucci,

M., and Vazquez-Aguirre, J. L. (2006), Global observed changes in daily

climate extremes of temperature and precipitation. Journal of Geophisical Research, 111(D5):D05109+.

6) The vertical profile of the atmospheric warming is consistent with the human-enhanced greenhouse effect.

- Jones, G., Tett, S. & Stott, P., (2003): Causes of atmospheric temperature

change 1960-2000: A combined attribution analysis. Geophysical

Research Letters, 30, 1228

http://www.agu.org/pubs/crossref/2003/2002GL016377.shtml

All references above are confirmed by independent studies (maybe with the exception of #4, which is a quite specific branch and is unique AFAIK)

Also, atmospheric physics that explain what happens when you increase GHG concentration (optical properties of these molecules, their behaviour in the atmosphere, climate consequences) is pretty much textbook knowledge. Old and confirmed. The more specific bits, like quantifying climate sensitivity, has been tested through many different lines of investigation, and although error ranges are still pretty wide, they all converge to the warming of 3ºC ± 1.5 for double CO2. A good comprehensive study is

- Knutti, R., Hegerl, G. C., (2008), The equilibrium sensitivity of the earth's

temperature to radiation changes. Nature Geoscience, 1 (11), 735-743.

This figure in the paper above is particularly interesting, summarizing all the investigation lines and shoing the convergence in an easy way to grasp:

http://www.nature.com/ngeo/journal/v1/n11/fig_tab/ngeo337_F3.html

The controversy on this issue belongs essentialy to the non-scientific media and internet blogs. I gave references about this in the other thread:

http://www.researchgate.net/topic/Climate_Change/post/What_is_the_media_role_and_influence_on_Climate_Change

Based on those facts, its clear...very good indeed

Climate is being changed by both.

Human use of certain chemicals, burning of fossil fuels, cutting of forests and agriculture is changing climate.

The last ice of the ice ages is melting, and this is changing climate.

Thanks all for giving good comments.

The climate change is natural but the frequency of change that is no natural and is influenced by the human activities

Everybody (on the earth) has their views from their own framework and the lens by which they are looking, while talking about Climate change and human induced changes (ref IPCC vs anti-thesis publication from Liberty Press). Facts are well narrated by Prakash Nutiyal & Alexandre Lacerda. Glacial scale suggests that we are heading to a warmer phase of the earth's cycle, and some scientific observations suggest that human induced activities are accelerating warming of atmosphere.

Thing to consider - have we exceeded any limit which has not been observed earlier (e.g., highest temperature in last 30 years; its mean things happened of similar nature some years back also). There are so many examples of such nature.

The fact is that climate changes have occurred and do occur. They are due to interactions atmosphere / biosphere / hydrosphere, variations in Earth, lunar and solar orbit. Due a many types of chemical and physical interactions. Also it's true, of course, that we are releasing CO2 into the atmosphere, increasing global warming. But in my view, there are other points that are equally important to understand, but fundamentally easier to intervene, such as birth control, less polluting and renewable energy, reduction of excessive consumption, better economy based on new optic, etc..

In fact, we must change the system. The global warming can be anthropogenic or natural or both. If we receive a massive coronal explosion it's clear that we and many other species will die. So, what can we really do to use our resources wisely?

If the global warming is a natural process, this is mean you can keep using the natural resources like you want? To think..

James DeMeo has already mentioned the Little IceAge and the Medieval Warming (thank you), but could have also mentioned the Dark Ages and the Roman Warming.

A Graph of the last 2,500 years is available at

http://www.c3headlines.com/ice-core-data/

and a graph of the last 10,000 years is available at

http://joannenova.com.au/2010/05/gullible-rudd-steps-right-in-it/ ,

which gives some perspective on the variability of the Earth's climate and Al Gore's Hockey-Stick.

However that does not mean we can continue to use fossil fuels at the present rate. They are finite resources.

The world is overpopulated and the natural resources are not limitless. Overfishing and pollution of the oceans is already happening. Many species are facing extinction due to Mankind's effect on the planet.

You do not have to be a warmist to realize that we have problems that need solving, but not by using the IPCC's and Al Gore's methods.

One thing I want to say - the increase of frequency and severity of extreme weather events in a such short time undoubtedly give us an evidence of anthropogenic impact of climate change

Most of climate change discussions are carbon centric and are prescribed to explain the global warming. Oceans are the largest sink followed by primary producers; many theories have been put forward to explain the same in the lines of ecosystem level works. There are other grey areas like sunspots, meteorite/comet hits, recession of moon, volcanoes, biogeochemical cycles and earth’s inner core and mantle. Such studies if replicated on temporal dimensions could help us provide new insights and better understanding about climate on this blue planet.

Ala Overcenco,

The reason for the apparent increase in extreme weather is probably due to the improvements(?) in global mass media. It is only possible to tell if an event is statistically significant if it can be measured over an appropriate period. From what I have read about long term weather trends there is nothing to get excited about. See:

http://www.climateadaptation.eu/sweden/en#storms

If you look carefully you can find plenty of IPCC information that says otherwise but IPCC is a political entity trying to justify it's existence. The IPCC is still trying to justify the existence of it's 'Hockey Stick' that shows the rise in temperature for the last 150 years but carefully ignores the fact that there were three periods in the last 2500 years when the global temperatures were significantly higher than the present.

Isotopes do not lie and they reveal that combustion -- humans burning fuels at high temperatures are generating the composition of the carbon and nitrogen we find in the atmosphere today. There are too many climate change deniers on this discussion that ignore the isotopic reality and abrupt rise in measured carbon dioxide in the air since 1959. Human beings are through mining, land-use changes and combustion of coal, oil and gas at record rates altering the thermal capacity of the air to protect the earth from extreme, or unstable, climatic conditions. Your best source is David Archer, The Long Thaw, although Spencer Weart, The Discovery of Global Warming is also very good. Jeremy Legget's Carbon Wars are important sources you should consider. No other satisfactory evidence exists to explain the abrupt increase in heat trapping gases we have seen in the last century. Human fingerprints in the form of isotope ratios are all over the excessive vapor gases we now measure rising in the atmosphere,

See MArk Bush, Ecology text for the pollen analysis that also supports climate change we see today is a disturbance of the natural greenhouse , or background thermal envelope, by human industrial wastes. See James Lovelock, the Revenge of Gaia and Ross Gelbspan, Boiling Point for a quick look at how we got to where we are today.

Clive Williams

I know, a lot of common people, selected scientists and even reserch institutions say about political conclusions of IPCC, but by my research experience in this field (from 1998, and even now I'm dealing with temperature extremes) there are no doubts about anthropogenic cause of climate change. Even more, namely the speed of a such change says about human impact on changing of atmoscperic circulation. Of course you can say that it is thanks to more larger and more precise instrumental observation, but namely based on a enough long time-series of temperature records (more than 200 hundred years) a lot of independent reserachers make such conclusions.

Seriously, are we still at this stage of the discussion? There are some disagreements with the conclusions of IPCC and other bodies and individuals. But there is a lot more substance to their conclusions than the naysayers will give the IPCC credit for. Is climate change happening? Absolutely! Within the technical definition of climate (30-40yrs span) we cannot deny the changes in the climatic patterns. is this occurence novel? No. The earth has experienced similar occurence before. So what is different? This is the crux of the climate change debate. It is not that the earth does not undergo this cycle of changes. It is whether human activities is catalyzing the process and making it worse. I believe the evidence so far that human impacts are contributing in no less a way to current climatic changes is hard to disagree with. I have worked with many rural communities and they can tell you about the changes going on. While their memories do not transcend their life time, they can tell you what has occurred and how some local activities have impacted their micro-climate. Now it is not too difficult for them to extrapolate that to the global level. As to whether current climate change is going to be long or short lived, I dont know. But I sure believe that we can minimize the occurence by adapting best practices.

Nature by itself has its own forces of change.But that is ususally gradual and takes time to have any impact on life.But Ma's activities ranging from slash and burn method of farming shifting cultivation ,release of large quanties of carbon 2 and carbon 4 oxide in to the atmosphere had caused ageneral change in the atmospheric temperatures.Areas onces cool are now hot because vegetation has been cut down and daily/annual precipitation has drasticallly reduce due to poor hydrological recycling.

As result the natural forces of climate change exists but Man's activities are rapidifying the process to limits that are creating social and economic embarassment to Man

I think the discussion is missing the mark. Science proceeds by constructing theories and these theories hold until a better one displaces them. It has been known for over 100 years that atmospheric CO2 absorbs heat. We have accurate measiurements that atmosphgeric CO2 is increasing and we know that release of old carbon from fossil fuels is contributing to this increase. Furthermore, we know from ice core records that past CO2 and CH4 levels have been positively associated with temperature. It is not unreasonable therefore to suggest that modern warming is caused by mankind. In the past, warming events were caused by external forcing such as solar activity, changes in the earth's orbit etc. However, to explain current warming by external forcing requires an explantion of why the stratosphere is cooling rather than warming as external forcing should lead to a warmer stratosphere. Consequently, there simply is not a better theory yet to replace the man-made greenhouse warming theory.

I would also like to say that measurements of environmental change are robust, particularly in the Arctic where change is particularly fast and measurements of multiple environmental factors overcome potential errors of instrument change when measuring just one (see for example Callaghan et al 2010 in Geophysical Research Letters).

Finally, I would like to defend IPCC. This is a rigorous process led by experts and the work is reviewed by experts. Rather than simply decry it as a political process, I would like to see examples of where data and interpretations are incorrect - if there are any.

So the bottom line is, to change our current understanding provide better evidence and better theories rather than simply criticise the established ones.

I’d like to second Terry Calaghan above.

No accusations of malpractice will change the fact that greenhouse gases obstruct infrared radiation, with its implications to global temperatures and climate, much like no embarrassing letters written by Isaac Newton could overturn the Law of Gravity.

To keep it simple, I think it would be fairly accurate to narrow it down to two main points:

1) We (humankind) pour some 30 Gigatons of CO2 every year in the atmosphere, which is more than double the annual atmospheric increase (the rest is mostly absorbed by the ocean).

http://en.wikipedia.org/wiki/List_of_countries_by_carbon_dioxide_emissions

2) Many independent studies, lead by different countries, in different generations, using different approaches, converge to the figure of a climate sensitivity of 3ºC ± 1.5 for double CO2.

http://www.nature.com/ngeo/journal/v1/n11/fig_tab/ngeo337_F3.html

It's a pretty straitforward calculation: we are raising the concentration of atmospheric greenhouse gases and we have a pretty good idea what happens when we do so. Stolen emails, Medieval Warming Period*, accusations of political bias are only irrelevant diversions. If one of those two facts above were untrue, this could be shown by proper science, not by a heavy-breathing Fox News presenter’s claims. It's a compelling set of data that does not depend on one scientist, one institution or one country.

If someone feels this is not true, I invite him or her to check the data where this belief came from. Did it really show clear evidence that we do not emit that much greenhouse gases? Or did it really present evidence that greenhouse gases do not affect the Earths temperature? Or was it just some clever fallacy, like “it was natural then, it must be natural now”? (by the same reasoning, an attorney could say “people die from natural causes all the time, therefore my client can’t possibly have killed the victim”…)

I’m sure ResearchGate has an audience that can resort and understand scientific evidence in a better way than the average blog. Let’s make good use of this.

*By the way, the existence of a warmer MWP would only indicate that the Earth's climate is even more sensitive to perturbations. It would, in other words, strengthen the case for mitigation now.

And thanks to A.T.J. Laat for the comment. I'll try my best to make good use of it.

James DeMeo,

Calm down. I think all you have to do is click on the link "Show full discussion", right below the "Most Popular Replies", on your right hand side. ResearchGate seems to automatically hide older comments when the discussion gets long enough.

Anthropogenic climate change is an inadequate question. This is not to deny human impact on the climate. Yet volcanoes have been responsible for injecting vast amounts of climate changing gases and solids in the past, and many such natural phenomena are out of the human brief. The questions that we seek to answer are; first is their and atmospheric ideal, and secondly, if we can agree on an ideal, what can we do as humans to achieve it.

Reduction of pollution, assiduous impact testing prior to the widespread adoption of practices or products, and polices which balance regional hydrology are the keys to climate management...eschewing blame.

A.T.J. Laat,

I could not find the full text of that paper in the internet, but I'll replace my sentences "Troposphere is warming while stratosphere is cooling. This too is consistent only with an enhanced greenhouse efect" by "The vertical profile of the atmospheric warming is consistent with the human-enhanced greenhouse effect."

I hope that would be more accurate. Please feel free to comment.

It is not like egg and chickn. Everybody knows that everything is connected with everything else, then why is there hesitation to accept the proposition that we are passing through anthropogenic warming period. Shivaji Chaudhry has recounted all possible causes of the climate change or warming and cooling periods on the Earth. Does anybody have evidence that one of any of them has happened on such a scale to generate such a warming level. If there is no evidence of such a cause at present or near past, all the causes enumerated by Shivaji are excluded and safe conclusion is that human activities are the cause of the climate change we are experiencing be it socialist agenda or something else.

True, climate change or short cooling and warming happened on the Earth in historical and archaeological past.

There evidence is also found in mythology. A renowned Indian professor of geography, (Late) SM Ali in his book "Geography of Puranas" attributes whirling Ganga in the hair locks of Shiva to the Ice age, similarly the growth of a fruit (rudra raksha) of humid tropical tree found in lower Himalayas from the tears of eyes of Shiva who could not close his eyes in search a Demon may be attributed to warm period. As an estimate it could have happened from 6000 to 7000 years from now. Geomythology has now become an established field in historical disasters studies.

These periods might have their valid reasons at those times as widespread volcanic activity or solar activity but CO2 released by human activities. In the absence of any natural cause it is quite legitimate on the part of a number of contributors to conclude that present climate change is the result of our own doing.

Precautionary principle requires that we accept it so that adaptation and mitigation strategies could be developed with committed endorsement of scientists and political leadership.

http://the-scientist.com/2012/07/20/climategate-case-closed/

Off course climate change happened for anthropogenic reason. Population is the key facor, incresing population increases the uses of technology, modern life, urbanization, industrialisation over environmkent, so ultimately climate is changing cycling order. It must be , we cannot avoid it but we should minimize it.

Alex Lacerda is right. I am a Plant Scientist specialising in biophysics and photosynthesis. Hence I would not know anything about CO2 or infrared absorption of radiation by CO2. I am 58. When I was born [CO2] was 314 ppm, it is now 397 ppm (up 26%) and will be 476 ppm (+51%) when I am 80 in 2034. Most people just do not understand exponential growth: that is why they cannot understand population growth curves or CO2 data (the anti-hockey stickers). It has been known that CO2 strongly absorbs IR since the days of Tyndall who happened to publish his work the same year Darwin did (1859). I cannot see how warming could not be occurring. As for CO2 being merely plant food: that is pathetic. Photosynthesis is not related linearly to [CO2]; it is a saturating curve called a Michaelis-Menten curve (elementary biochemistry). Hence a 25% increase in CO2 does not lead to anything like a 25% increase in photosynthesis. That is 1st year biology stuff (I know I have taught it). Increased CO2 in the atmosphere is natural? Fossil fuels are ancient and so have no 14C and their 13C/12C isotopic ratio is different to the modern atmosphere (as preserved in 18th and 19th century wood and in arctic and antarctic ice). Anyone with a mass spectrometer can tell you that the isotopic ratio of the atmosphere today indicates massive injection of CO2 from fossil fuels. It cannot be C from peat bogs or from oceanic turnover because such sources are modern in C14, C12 and C13 signatures. Add to that the massive deforestation going on and the mobilisation of carbon in Nth hemisphere permafrost regions from peat bogs and increases in atmospheric CO2 will overrun the capacity of photosynthesis to absorb it. Absorption by the oceans is also too slow to pull atmospheric CO2 down. Global human impact is frightening. Consider this. Global photosynthesis can be calculated fairly easily from the Kealing data. A frightening amount goes through our bellies. That does not take into account all the C humans use for non-food like wood. And finally older astronauts comment on how different the world looks to what it did when they were first in space. That tells you something.

The Berkeley Earth Group (see http://berkeleyearth.org/) sought to provide a definitive, objective assessment of temperature and they concluded in October 2011 that the measurements carried out by other agencies were "done carefully and that potential biases identified by climate change skeptics did not seriously affect their conclusions". This assessment used 5 times the number of measurements of previous studies and prior to its implementation, both skeptics and those in agreement wirth IPCC findings confirmed that they would abide by the findings. That some skeptics continue to confuse the issue, primarily with support from the fossil fuel industry, means that they do now justify the designation of "climate deniers". What does need more research is the influence of anthropogenic land use on climate change and how it interacts with the impact of anthropogenic greenhouse gas emissions at both micro and macro-climate levels. The accelerating degradation of land, biodiversity, forest and marine resources also increases vulnerability to the current and inevitable future impacts of climate change, as summarised in the recent UNEP GEO5 report (see http://www.unep.org/geo/pdfs/GEO5_SPM_English.pdf)

Yes, really climate is changing by human activities and at the same time it is changing naturally natural phenomena.

At this point does it really matter any more? We have climate change and need to address anything that we can to mitigate the changes, regardless of cause at this point. Scientists should not even have to bother themselves with this part of the topic.

To Bev: if you do not understand the reason of the sickness there is no point to treat the consequences. As all the colleagues commented above, the reason of fast climate change is anthropogenic CO2 emissions which actually have to be addressed (not the temperature rise or precipitation patterns change or see level rise).

To Tarasova:

Firstly, send to you my greetings, secondly, the opportunity that you understand that is no reason that the climate changes occurring (phyto-climatic, it is my personal concept), they are complex fenomente naturally occurring in one hand and the performance of activities human on the other or their place in complexity, and I totally agree with you that precipitation, temperature, sea level rise, and so on are products provided these phyto-climatic changes. I studied a lot years in biophisic and physic environemntal components in this area, but it is difficult to quote the reason of the of the sickness there is no point to treat the consequences, since diseases are only one part of product, so is therefore not due. You quote that the reason of fast climate change is anthropogenic CO2 Emissions, which actually have to swear addressed (not the temperature rise or precipitation patterns change or see level rise). Somewhat agree but besides anthropogenic CO2 emissions are also other causes of factors. In order to know causes, effects relations were on our situation analyzing, based on the groups and of stress factors (Lushaj, 2005), bag of their influence on basic, and concretely:

• Predisposing Factors (Long Term Factors);

• Inciting Factors (Short Term Factors), and

• Contributing Factors (Long Term Factors) etc...

Blade runner is a movie from the 80's about L.A. at about now. It was a great movie, but in watching it today you can't help but realize how wrong we all were about the future. In the movie air pollution has gotten so bad that you never see the sun, and it rains all the time. I lived in L.A. back then, and it the movie seemed predictive, of an inevitable future. Smog and ozone alerts everyday, wall to wall traffic of large smoky cars.

Well I was just out in L.A. and the sun is shinning, and the air is clean. My point is of course we should eliminate pollution, mitigate problems, and move as quickly as possible off fossil fuels. Not just for the planet, but for ourselves and our children. But we live in an age where many people make their living by scaring the rest of to death. I'm reminded of the novel Angela's Ashes, where a young catholic boy grieves when his protestant friend dies...because his friend won't get into heaven. Science is generally seen as an improvement over religion, because it is less certain, less dogmatic. An important rule of science, is to let your conclusions only reflect the actual resolution of your data.

Climate is changing and It's not solely because of human activities but because of nature as well.The Earth is dynamic in nature and climate changing has been reported to many times in geological history of the Earth.

We could have easily got to the kind of future described in the previous post if have not made people realizing it. The measures have been taken and we avoided getting there. You can read abou the history of LRTAP convention and how drastic were the reductions of SO2 and ozone precursor emissions since 80-s (http://www.unece.org/env/lrtap/).

Unfortunately people are unlikely to take drastic decision unless they are "frighten to death". Comfortable life is not very encouraging for actions even if objective assessment shows that actions have to be taken.

http://www.youtube.com/watch?v=bbgUE04Y-Xg

My first apartment was in a seedy section of Indianapolis, IN. It was one of those U shaped buildings, popular in the 40's. One day as I was comming home, I startled a large gray rat was crossing the mouth of the U. The rat scurried to hide right near the building entrance. I had no interest in this creature so I planned to ignore it but the rat was not so sanguine. As soon as I approached it began to hiss and growl, in a most fearful manner. I was frightened and ended up killing the creature with a brick.

My point is that panic often leads to sub-optimal solutions. Today, billionaires like Branson & Gates are exploring funding large scale solutions to climate change such as ocean seeding, or adding chemicals to airline fuel that will hopefully ameliorate CO2 buildup in the atmosphere. While countries such as China are investing in huge projects, such as the three gorges dam, to overcome water and energy problems.

While I applaud all efforts at accommodation, the potential impacts of these large scale panic solutions may prove dire in the long run. The un-intended consequences of these programs are frightening. Some research shows that, for example, large dams may be in part responsible for earthquakes in distant regions. Mankind has a deep history of panic solutions that begin a spiral of problems. A good example is how regional biodiversity has been impacted by the introduction of foreign species to solve problems.

These efforts at massive solutions tend to overshadow the smaller, testable solutions, that have proven successful in the past.

For example drought is a problem that is affecting many in both the developed and developing world. Global solutions are now being explored, and everyday the media add fuel to the fire under quick solutions by presenting people with scientific data without proper context. This week is the loss of the Greenland ice sheet.

While smaller solutions, like encouraging the transition from English style grass lawns to climate stabilizing poly-cultures are laughed at or ignored.

My company, has proposed a series of these small regional solutions, driven by our unique form of environmental energy, that could slowly change regional hydrology.

My fear is that our environmental problems are fast approaching a tipping point. Not the tipping point that the media and the scare industry is promoting, where global warming begins to run out of control. But instead the tipping point where drought, wildfires, and agricultural disasters and the media hype, panic the silent majority into supporting un-testable global solutions.

O. Tarasova

I sympathize with your sense of urgency. Actually, we should be at least slowing down emissions at this point, but all we see is still acceleration. Certainly, denialism has a huge role on this, be it wilfully orchestrated or simply a reaction of human nature.

But “scared to death” seems to be the wrong mood for action. And I’m sure you don’t mean exaggerating facts: the truth on this subject is already scary enough.

Beth Gardiner wrote an article recently on this subject, and her analysis “feels” right to me: she says that “we block out complex problems that lack simple solutions”. I think that’s right. People just don’t want to be bothered with a highly complex problem to which they individually can do so little. Specially if the disinformation campaign on the media demands that the public actually study and understand physics to sort out fact from rubbish. In this context, fear mongering sounds counter productive, because they reinforce the blocking out of the problem.

Our society is designed to largely delegate this kind of analysis to experts and policy makers. It’s just that this time, lobby is making policy makers wait for public pressure to make their decisions. The result is all the inaction we’ve seen so far.

We’re drifting off-topic here, but it’s an exciting and important subject. Maybe it would even deserve a topic of its own.

Here’s Gardiner’s article. Well worth a reading:

http://www.nytimes.com/2012/07/22/opinion/sunday/were-all-climate-change-idiots.html?_r=1&ref=science

Gare Henderson,

I agree. Big geoengineering solutions are risky moves that are likely to cause other unforseen problems. Actually, many of these problems are foreseen.

The safest and most elegant solution, in my view, would be a gradual phasing out of fossil fuels, through internalization of their true costs (environmental, health, national security, etc). By gradual I mean a slow, multi-decadal transition. Plenty of time to develop technologies, improve the existing ones, achieving mass production scale and reduction of costs.

Not to mess up is usually cheaper than fixing, speacially in such a complex system.

I am not an expert, but I suggest you the paper by Dim Coumou & Stefan Rahmstorf on Nature Climate Change journal (http://dx.doi.org/10.1038/nclimate1452), and the references within, who have analyzed the recent extreme weather events and if they are linked to anthropogenic global warming.

If the present climate is so hot, how do you account for the following?

A high glacier between high pass Switzerland and Italy melted and revealed that it had previously been a trade route.

The details showed that there have been five warm periods in the last 4,800 years including the present warming.

The article was published in Die Welte, 14 Nov 2005:

http://climateaudit.org/2005/11/18/archaeological-finds-in-retreating-swiss-glacier/

A Conference was held at the University of Bern in August 2008 to present and discuss the findings:

http://www.geo.uzh.ch/~snus/publications/schnidejoch.pdf

Human activities certainly influence natural variations. There is unequivocal evidence based on isotope ratios that accumulating heat trapping gases in the air and oceans are from combustion of fossil fuels and land-use changes that humans make in order to urbanize, transport, farm or deforest large areas of the arable surfaces of the planet. AN earlier writer is correct, this is really the wrong question.

Our focus should be on averting risks, preventing public health problems associated with extreme weather events, tropical diseases, and sanitation among the most affected populations. Humans are disrupting the earth's thermostat which for 10,000 years has regulated swings in temperature and the build-up of heat trapping gases has raised carbon dioxide levels to a range not seen in 800,000 years when the planet was warmer than now. David Archer's books are the best source of reading to answer some erroneous posting on these pages. We need to have discussions on adaptation and mitigation of climate change and not keep asking questions easily answered by more than a dozen authorities, who have authored book-length explanations of how human agency has altered the atmosphere, oceans and arable landscape.

for a start see--

http://myweb.rollins.edu/jsiry/glodex.html

Alex Chausson

For a broader perspective, the FAO Food Price Index on the link below. Prices seem to oscillate more wildly lately.

http://www.fao.org/fileadmin/templates/worldfood/images/home_graph_3.jpg

Yes, this is more to the point. I might add -

How can we replace, or instill true character into, politicians who do not accept or proclaim the reality of our best scientific understanding?

Isn't this too late to discuss here? of course nature contributes to climate change but the most important fact to be understood is nature has the resilience to adapt to the change it is causing over the time. Historically there are few major natural shifts are seen and there we have seen also drastic changes in the structure of the planet and distribution of lives. Here I think the ficus is how excess contribution is made by the human being that is pushing the climate forcing beyond it's traditional carrying capacity/resilience. Here I suggest a recent article - Little long but very learning work by Bill. Here is the entire story: http://www.rollingstone.com/politics/news/global-warmings-terrifying-new-math-20120719

Perhaps Tim Flannery's Book, THE WEATHER MAKERS: HOW MAN IS CHANGING THE CLIMATE AND WHAT IT MEANS FOR LIFE ON EARTH (2005, Paperback edition 2006), published by Grove Press in New York, may throw some light on the question.

Human industrial activities are believed to be adding to the amount of "greenhouse gases" naturally present in the atmosphere. There are mounting proofs that following the industrial revolution of the 18th and 19th centuries, which commenced in Britain and expanded to several parts of the world, the amounts of carbon dioxide, methane and other greenhouse gases in the atmosphere has increased somewhat. Greenhouse Gases (ghg) released from human activities or natural sources and trapped in the atmosphere acting as blanket preventing the earth's heat from escaping into space, thereby increasing the earth's temperature, creating variability in the world climate (Climate Change). To know more about ghgs, follow the link Greenhouse Gases. As a result of the increasing temperature, our earth warms up - a phenomenon referred to as Global Warming. Since the start of the industrial revolution of the 18th century, the temperature rise has been on the upward trend and it is believed that it will continue to rise. This lends further credibility to the scientific conclusion that humans are contributing to Global Warming. Global warming comes with a lot of consequences (see Evidences & Effects of Global Warming)

Based on scientific results and day-to-day physical evidences, global warming (caused by humans) is no longer in dispute. With the the verdict of the fourth assessment report on climate change prepared by the Intergovernmental Panel on Climate Change (IPCC), there is also very little contention that man contributes to the heating up of the Earth. However, the question that remains is: how much of the warming is caused by man?

Alexandre Lacerda and Terry Callaghan are quite correct and the repeated focus on this aspect of the questioning of human induced global atmospheric alteration misses the important focus we ought to pursue: ways to mitigate what we are doing and adapt to the consequences of what we have done. As early as the 1850s (George Perkins Marsh, Man and Nature 1864) Marsh recognized the role humans have in altering regional climatic conditions through deforestation, and creating deserts where once grasslands persisted, despite natural disturbances.

The discussion we are having here should be on human responsible actions to alleviate the costs and damages inflicted on people unprepared to deal with desertification caused by a shift in rainfall and wind patterns. In Mail, Nigeria, Darfur and Ethiopia, th conditions are clear and compelling, abrupt climate change has real impact on grasslands, herding, transhumance and marginal farming where irrigation is required. In Australia, Pakistan and Siberia the sorts of landscape changes due to climate shifts are as startling as they are costly. For going on two centuries scientists and geographers have been aware of the power of humans to alter the landscape, and now the oceans and atmosphere are showing signs of human-induced chemical alteration. How we act in response is more important a question than precisely how much of the changes we see is due to deforestation, industrial combustion, and desertification. When you discover you have diabetes, or cancer, or chronic heart conditions do you wonder what percentage is due to your diet and habits or do you treat the condition and worry about the attribution to behavior after undergoing the appropriate therapy?

Climate change is a natural phenomena influenced and enhanced by human activities...

Yes, climate change is a natural phenomena influenced, enhanced and combined by human activities.

To the scientific community the question on anthropogenic climate changed has been answered. Yes it is caused by humans, as no 'natural' drivers can be found that account for the changes recorded. As stated above by a number of people this answer does not negate the fact that natural changes occur, and the fact that natural climate change has occurred in the past is a bit of a red herring, since anthropogenic climate change cannot have occurred pre-historically. Therefore natural, historic, changes to climate cannot negate the possbility of an anthropogenic cause. However, I am often seeing this argument used against anthropogenic climate change.

The real question we need to answer is how do we deal with the 'need for a balanced perspective' used in the media and promoted by a small minority of well funded people or institutes that are not related to the science of climate change.

As a scientist I believe it is our duty to educate and we should not shy away from contentious issues - but present the available facts. I regularly use this web site to find the latest information on the climate issue:

http://www.skepticalscience.com/

Graham, "natural changes occur, and the fact that natural climate change has occurred in the past is a bit of a red herring, since anthropogenic climate change cannot have occurred pre-historically"

That is a strange line of reasoning. We are still recovering from the Little Ice age which appears to be part of a ~500-year cycle that shows up in ice core graphs.

the temperaure 2300, with a peak about 3,400 years ago that was even warmer than the Roman Warming about 2,200 years ago.

see: http://wattsupwiththat.com/2009/12/09/hockey-stick-observed-in-noaa-ice-core-data/

There is certainly anthropgenic pollution and we do need to reduce fossil fule consumption.

I commonly hear the argument that since there was historic climate change, then current changes must be due to 'natural' causes and not due to people. This is false as an argument, even if the current changes were due to natural variation. Alexandre Lacerda points out some of the reasons that point to AGW that are independent of the historic tempaerateres.

It is also pointed out that historic natural variation has been much greater than what we see now, with the unstated tag line of therefore we don't need to do anything. However, our current societies and economies were not around then. We need to understand how the current changes will affect our current society. The recent and forthcoming increase in food prices due to heatwaves, droughts and floods during this year are a case in point. Now I'm not saying that this is entirely AGW, but some, as yet unknown, proportion of such extreme events must be due to AGW. This bears an economic cost. Therefore it is an avoidable cost - even if some of the climate change is due to natural variation.

Some people are now arguing that the economics are in favour of going green for this reason, but nonetheless the long term economics are in favour of using less carbon, particularly if we move away from the short-term economic discounting rates.

So, in summary, the long term historical climate data is not relevant to our current situation. Current changes in temperature are due to both natural and human forcings and the longer-term consequnces of climate change (just take rising sea levels, or lack of water for a billion people that rely on Himalayan glaciers, for example) surely mean that we should work to counter such changes. Minimising our forcing on the climate appears to be the only humane approach.

The climate changes naturally, in fact it is normal, the Universe changes naturally. Throughout the life of the Earth have seen great climate changes.

But the actual climate change we are experiencing is caused by antropic activity.

Yes, climate change is a natural phenomena influenced, enhanced and combined by human activities.

Mario Gonçalves,

There are already a number of attribution studies that focus on that subject. Examples at the end of the comment (references 1 and 2).

To keep it simple, it would be hard to explain how could we add so much radiative forcing to our climate system and NOT cause any significant change. We added enough CO2 to the atmosphere to add as much as 1.5 W/m2 to the climate (ref 3) since the Industrial Revolution. As an element of comparision, the largest estimates of the diffference between the solar forcing at the Maunder Minimum (Little Ice Age) and today are in the ballpark of 0.5 W/m2.

And the test of time seems to support the present science: IPCC projections from the 90's compared to subsequent observations (ref. 3) show a very good match - except on some cases where the IPCC was too conservative: Arctic sea ice and sea level rise are worse than projected.

1) Stott et al. 2000

http://funnel.sfsu.edu/courses/gm310/articles/GlblWrming20thCenturyCauses.pdf

2) Meehl et al. 2004

http://journals.ametsoc.org/doi/full/10.1175/1520-0442%282004%29017%3C3721%3ACONAAF%3E2.0.CO%3B2

3) http://data.giss.nasa.gov/modelforce/

4) Rahmstorf 2007

http://www.pik-potsdam.de/~stefan/Publications/Nature/rahmstorf_etal_science_2007.pdf

Climate change is natural phenomena. Throughout the geological history Mother Earth has experienced many drastic changes in climate,however human activities are also responsible for climate change partly. Increased industrialization has been contributing more in climate change for few decades.

The question was: "Is climate really changed by human activities or is it changing naturally?"

"Is climate really changed by human activities", Well yes, as long ago as George Perkins Marsh's 1864 book Man and Nature the diplomat and historical geographer Marsh noted how humans altered local climatic conditions due to deforestation and drainage. In that same century Fourier and Arrhenius postulated that carbon dioxide gas in the air traps long wave radiation, thereby heating the earth.

Both Gail Christianson's book and Spencer Weart's book are excellent accounts of the history of how scientists discovered that humans are changing the climate and chemistry of the oceans.

http://myweb.rollins.edu/jsiry/Christiansonbooknotes.html

http://myweb.rollins.edu/jsiry/WeartOnWarming.html

The part of the question that asked, "or is it changing naturally?" is not as significant as it may appear, because the word natural has a variety of meanings. So wide is the meaning that one may imply by the term "climate change is natural," that there is nothing humans do to alter conditions of land-cover, or chemistry, or radiative forcing.

As Marsh suggested in 1864 humans have the force equivalent to natural tectonic agents or glaciers in the power of our population and technology to alter geography, atmosphere and oceans. And this alteration we are now experiencing will persist for decades if not centuries because 1) carbon dioxide remains volatile in the air for at least a century, and 2) the thermal expansion of the oceans at the surface and at depth will take centuries for the temperature to fall back to what it was even fifty years ago because of the high specific heat of water bodies.

Hola Mario,

"You are missing the point here. Is the atmospheric CO2 rising responsible for global warming?" I have seen no proof that the rise in atmospheric CO2 is due to the rise in

ocean temperatures or vice versa. It can be argued that a rise in ocean temperature will cause the oceanic CO2 to evaporate more readily and it is the cause not the effect.

The climate was always changing in the past too. The history says that the desert areas of RAjasthan in India were green and having rivers and ports but now have been converted into desert. Tus climate change happens naturally. However, human activities (industrialisation and unsustainable development) have worsened the situtation.

add to previously entered answer. Jack Bennett

According to me, climate is changing naturally, and human activities are speeding up the process.

There is a concept called entropy, which states that everything in the universe moves from a state of order to disorder. So, the climate is changing.

Human activities like the emission of harmful gases into the atmosphere speeds up this process.

Well, I think that the change is due to the Sun, solar irradation. The problem is that we consider the acction human for this issue, so it is necessary to review it.

I must say that "Terry Callaghan · 22.34 · Royal Swedish Academy of Sciences

I think the discussion is missing the mark. Science proceeds by constructing theories and these theories hold until a better one displaces them. It has been known for over 100 years that atmospheric CO2 absorbs heat." hits the mark exactly.

No other hypothesis accounts so well for the global patterns now documented in ocean temperatures and acidity, droughts and extreme weather patterns, not to mention the disrupted timing of insect larval development and flowering plants. The real question we should be asking is: to what extent will mitigation not affect the human driven abrupt climate changes we and others are experiencing and how can human populations best adapt, humanely and fairly to the pervasive and difficult to remediate disruptions that climate change due to combustion of carbon fuels has triggered? We have an obligation to explain to people that their are risks to our continued reliance on fossil fuels and centralized electricity production. We need to move off of this question to a better use of our combined speculative wisdom on how best to adapt to and how effectively we may mitigate the impacts of an unprecedented, swift, and relentless rise in carbon dioxide emissions.

I believe the question is not quite formulated properly. Factors driving climate variability can be divided as "external" and "internal". External factors are natural: the solar cycle, volcanic eruptions, and man-made: anthropogenic emissions increasing the concentration of greenhouse gases. "Internal" variability is the result of interactions between the climate system subcomponents: atmosphere, ocean, cryosphere. So the short answer to the question is that climate change is driven by BOTH human activites AND by natural factors.

Yes, climate change is a natural phenomena influenced, enhanced and combined by human activities. From my studies I have divided into steress factors (Lushaj, 2005), bag of their influence on basic, and concretely:

"External", as are natural: the solar cycle, volcanic eruptions etc. and "internal", that I have divided into 2 "subinternal" groups, as: firsstly, atmosphere, ocean, cryosphere, etc.and athe the same time second, as man-made: anthropogenic emissions increasing the concentration of greenhouse gases.

At the same time for the same study, in continuing of my studies I have and other clasification, by:

• Predisposing Factors (Long Term Factors);

• Inciting Factors (Short Term Factors), and

• Contributing Factors (Long Term Factors) etc..

keeling data from hawai observation and IPCC data are enough evidences to prove climate is changing due to human interferances not naturally as it was in the geological past

Problem!

Ishfaq Mir

My alternative is for both! ...

My alternative is for both.

There are several controversies about climate change. but there are some studies which say us about climate change.

Intergovernmental Panel on Climate Change (IPCC) 2007

Main article: Intergovernmental Panel on Climate Change

In February 2007, the IPCC released a summary of the forthcoming Fourth Assessment Report. According to this summary, the Fourth Assessment Report finds that human actions are "very likely" the cause of global warming, meaning a 90% or greater probability. Global warming in this case is indicated by an increase of 0.75 degrees in average global temperatures over the last 100 years.[13]

The New York Times reported that “the leading international network of climate scientists has concluded for the first time that global warming is 'unequivocal' and that human activity is the main driver, very likely' causing most of the rise in temperatures since 1950”.[14]

A retired journalist for The New York Times, William K. Stevens wrote: “The Intergovernmental Panel on Climate Change said the likelihood was 90 percent to 99 percent that emissions of heat-trapping greenhouse gases like carbon dioxide, spewed from tailpipes and smokestacks, were the dominant cause of the observed warming of the last 50 years. In the panel’s parlance, this level of certainty is labeled 'very likely'. Only rarely does scientific odds-making provide a more definite answer than that, at least in this branch of science, and it describes the endpoint, so far, of a progression.”. http://en.wikipedia.org/wiki/Scientific_opinion_on_climate_change