Dear Sumanta, you are asking a complex question for which there might be no exact answer today. While in economic literature the statement about temperature growth in the last 100 years by only anthropogenic influence dominates, physicists are still in doubt; see for example https://www.newscientist.com/article/dn11639-climate-myths-the-cooling-after-1940-shows-co2-does-not-cause-warming/ . There exists also a hypothesis about global cooling, but on much larger time scale; see http://isthereglobalcooling.com/ . The graph about global temperature and CO2 dynamics is the last 450,000 years is attached (from this source). If this graph is correct, we have an interesting observation: warming went faster (about 10,000 years) than cooling (100,000 years). It is unclear whether triggering is caused by some shocks or some mechanism of dynamic equilibrium on the Earth. But is is also clear that we observe anthropogenic contribution to this process for the 1st time.

The problem however is that we cannot wait too long without making actions to combat global warming. Less carbon emissions would indeed work towards speed reduction of this process, but it might happen that other greenhouse gases (like methane) will continue working in its favor while increase of volcanic activity (observed in the last 10 years) will work towards reduction.

As for the rise of ocean level, the effect is still small today, and is caused not so much by ice melting but more by change of water density with temperature and salinity. However, melting of all Antarctic ice will cause a catastrophic rise of the ocean level by 60 meters; see https://nsidc.org/cryosphere/quickfacts/icesheets.html . Melting of Greenland will have much lower effect (6 meters), but here we observe catastrophic melting in the last years.

@ Kenneth M Towe sir, the article you have referred in response to global salinity changes has tried to reconstruct the trend in short to medium term (Year 1950-2008). I am more interested to know any details of it if available for a much longer period say hundreds to thousands of years if not millions... So that we can corelate it with other sets of data e.g., earth history and sea level changes. I appreciate your valuable response though. Thank you.

Sir, so you think variation of carbon (C) concentration in the Earth's atmosphere (as CO2) is the catalyst of change. Assuming most of the other things are either seasonal or more or less constant.

But our planet has experienced multiple ice ages from Precambrian period's snowball earth to most recent ice age event that occurred about 15,000 years before present. And during the Boring Billion (of evolution of Earth) probably nothing changed for a considerable longer time. Therefore the question remains... Why the frequency, duration of ice ages, and the time lag (gap) between two glacial periods vary considerably?

In my opinion, natural in-out flux of carbon in atmosphere may not be the reason of change (or the only catalyst) of global climate. Otherwise it would have been much more predictable or at least the variability in time lag should have been reflected based on duration of immediate previous ice age and its intensity. I would appreciate if you or anyone working in this field shed some light on this.

Dear Sumanta, you are asking a complex question for which there might be no exact answer today. While in economic literature the statement about temperature growth in the last 100 years by only anthropogenic influence dominates, physicists are still in doubt; see for example https://www.newscientist.com/article/dn11639-climate-myths-the-cooling-after-1940-shows-co2-does-not-cause-warming/ . There exists also a hypothesis about global cooling, but on much larger time scale; see http://isthereglobalcooling.com/ . The graph about global temperature and CO2 dynamics is the last 450,000 years is attached (from this source). If this graph is correct, we have an interesting observation: warming went faster (about 10,000 years) than cooling (100,000 years). It is unclear whether triggering is caused by some shocks or some mechanism of dynamic equilibrium on the Earth. But is is also clear that we observe anthropogenic contribution to this process for the 1st time.

The problem however is that we cannot wait too long without making actions to combat global warming. Less carbon emissions would indeed work towards speed reduction of this process, but it might happen that other greenhouse gases (like methane) will continue working in its favor while increase of volcanic activity (observed in the last 10 years) will work towards reduction.

As for the rise of ocean level, the effect is still small today, and is caused not so much by ice melting but more by change of water density with temperature and salinity. However, melting of all Antarctic ice will cause a catastrophic rise of the ocean level by 60 meters; see https://nsidc.org/cryosphere/quickfacts/icesheets.html . Melting of Greenland will have much lower effect (6 meters), but here we observe catastrophic melting in the last years.

Dear Kenneth, this is not one-to-one correspondence to give you an answer. We do not observe high sea level rise simply because small fraction of glaciers has melted over last 100 years when this change in ppm has been observed. Here (click graph) we have a record of change in global sea level; source: https://en.wikipedia.org/wiki/Past_sea_level . Those changes were not 30 cm, but on the scale of 100 meters. While for animals in the past this was not catastrophic (even for a hypothetical increase by 1 meter in 1 year - I guess it was much slower), for modern cities it would be.

Denial ain't just a river in Egypt. Mark Twain.

The Sun with its intense ray provides the necessary energy to evaporate water and starts/initiates the global water circulation. Then other factors are, 1) Rotation of the earth upon its own axis, 2)Orbital motion of the earth around the sun ,3) Gravitational forces of earth and sun /other celestial bodies, 4) Global air circulation. With this much stuff you can move ahead.

@ Radhashyam Sir, As per available/published records....Besides amount of sun's incoming energy [believed to be constantly increasing till date as being observed in other star's life cycle at their respective stages (!)] all other factors i.e., rotation speed of earth(!), orbital motion (earth's revolution), gravitational force (?) that you have mentioned are more or less constant. Though global air circulation are dynamically seasonal but the causes of its variation is itself under question. Then how they can be the catalyst of in-consistent changes of climate and water cycle? ....and, Who is actually driving them? Still unaddressed. Anyways, thanks to Kenneth sir, Yuri sir, and others for the valuable addition.

The key flaw in your formulation is that it is not a simple linear chain as you have outlined.  Almost all of the elements that you have listed are all interconnected and influencing each other.  There are also many other factors.  For example, your list doesn't include vegetation.  Vegetation plays both a role in solar energy flux as well as in hydrologic cycling and its interplay with water vapor's role.  3/4 of the Earth may be water covered, but that 1/4 that is rock (with or without vegetation) plays a big role in how energy moves around the globe and vertically in within the oceans.

Wide ranging climate change has been a perpetual feature of Earth for billions of years.  This is a fact that is often glossed over in current climate change discussions.  The dynamic equilibrium that you refer to is much more dynamic and wide ranging than is evident from what one reads in the mass media.  Anthropogenic CO2 is only one of many, many factors shaping global (and regional) climate.  It is significant, but it does not dwarf the others, and certainly doesn't dwarf them in aggregate.  It does perturb the system, and we might not like the results.

All. Could you please enlighten me.

Geological records show millions of years of alternative global warming, global cooling, high CO2, low CO2, high O2, low O2. Way before humans ever existed or became industrialized.

I don't understand why the current warming is attributed only to human activity.

Is this due to exclusion of other factors?

Mr.Sumanta Dandpath, as noted above in 4 points by me, these are the major change agents for anything and everything like water cycle, storms & cyclones, deviations on climatic behavior, earth quakes, tsunami to come up in this planet. Fifth factor ocean current is also playing a role to initiate/start any change on earth's surface.Excessive human activity has become now a headache for global warming.  

The current warming is not attributed exclusively to humans (at least not by informed people).  The entirety of human civilization has been during one long, natural warming trend.  There have been numerous shorter episodes of variation about that longer-term warming trend.  Some of these can be traced to factors such as volcanic eruptions and solar and orbital cycles.  The issue with anthropogenic warming is that human activities have produced a spike in atmospheric CO2 through both fossil fuel burning as well as land development (i.e. agriculture and deforestation).  This spike corresponds to a spike in warming.  Climate modeling supports the intuitive conclusion that the changes due to human activities are contributing to the current changes in global warming. 

If one takes the view that human activity is "unnatural" then one should conclude that the current rate of warming is unnaturally high.  If one were to instead view that human beings are just one of many species on Earth and are thus part of nature, then our impact would be just as "natural" as the methane produced by termites.

Regardless, we humans are capable of contemplating and understanding our impact on the environment.  It remains to be seen if we are capable of acting on that understanding.  Too rapid of warming, or too extreme of warming, will cause a multitude of problems for both humans and other species.  Thus, since the unwise, profligate use of fossil fuels is causing problems, most would conclude that we should be wiser and less profligate in our use of fossil fuels.  The modification of ecosystems by human development and agriculture is another branch of this problem that gets less attention than the burning of fossil fuels.  Given the fact that we humans are dependent on ecosystem services for air, food, and water, it would behoove us to strive to not "soil our nest" to the extent that it no longer supports us.  Warming is not the only global change that humans are a big part of.

Dr Stefansson,

It has been known since the work of John Tyndall in the mid 19th Century that CO2 is a greenhouse gas, i.e. it absorbs terrestrial radiation unlike N2, O2, and Ar the main atmospheric gases. The Industrial Revolution occurred when it was found that burning fossil fuels could provide the work done until then, by man (at times slaves), animals, water wheels and wind mills.

Burning fossil fuels produces CO2, and as shown by the ice cores, the atmospheric level has of CO2 has risen from a steady 280 ppm before the Industrial Revolution to 400 ppm now. . Since radiation from the Sun has been fairly constant then just as 2+2 makes 4, then it is obvious that the increase in CO2 is causing the current global warming.

You seem to be aware that CO2 and temperature have varied in phase in the past so it should be no surprise to you that if mankind increases the CO2 in the atmosphere then the result is warming.

Cheers, Al.

To answer your question #4, yes, there have been attempts to estimate the salinity of specific oceans in the geologic past.  The difficult part of this is that salinity is far from uniform across the globe. Because of these wide variations, estimating the global average through geologic time is difficult.  In the past, there have been large seas/oceans that had restricted circulation that resulted in massive deposits of salt/evaporties.  For example, my grandfather worked for years in a salt mine in a Permian aged deposit in Kansas that is up to 400 feet thick.  The salinity in some of these seas was very high, but at the same point in time there were likely oceans with salinity close to the modern average.  The current salinity of the oceans is a product of all this salt having been continuously sequestered into salt deposits over geologic history.  The process of this sequestration is part of the interplay between oceans and continents that I eluded to in my earlier post.

http://www.salinityremotesensing.ifremer.fr/sea-surface-salinity/salinity-distribution-at-the-ocean-surface

http://www.kgs.ku.edu/Publications/Bulletins/214/03_salt.html

Hi Al,

I am well aware of warming in the northern hemisphere, I am from Iceland. It has been experiencing higher temperatures. I am also well aware of what high CO2 can do to global climate. Just look at Venus.

But earth has gone through multiple warming/cooling periods before the industrial age.

I was only asking if the causes of previous global temperature shifts (before humans) have been determined and linked to natural causes like methane, ethane SO2 and h2o, which are more potent greenhouse gasses than CO2.

If so, then then there would be a stronger argument for ascribing the current warming to human activity. 

Take care, Stenni

Hi Stenni,

Most of the earlier climate changes correlate with changes in CO2, especially those of the recent glaciations. So there is no need to look any further than man made CO2.

The problem is that the climate models cannot replicate the last ice age nor the abrupt climate changes which happened as it ended.

https://nsidc.org/sites/nsidc.org/files/files/NRCabruptcc.pdf

So we may be in for an inevitable surprise When the Arctic sea ice disappears.

Cheers, Alastair.

@ Matthew Sir, Thanks for your constructive input. However, in my formulation I have only considered physical factors excluding direct biological contributions from living beings such as vegetation, animals etc. Though they also get influenced and make influence on global change but they are probably the outcome of changes and may not be the primary cause of it. Say for example... If whole earth was covered by ice/snow (e.g., during snowball earth or during some other ice ages) for a considerable longer time (much much longer than a few life cycles). In that condition, if they were either vanished or became inactive for rest of such cooling periods .....then how they could able to act to change the whole scenario to reverse it? (i.e., from global cooling to global warming) Therefore, I feel it will probably be the physical factors (may be some more factors than listed ones) that make and break the cycle to bring the global change. At the bottom of my question the influence of observed variability in concentration of Oxygen/Carbon-dioxide/Methane etc. is highlighted though.

Regarding long term salinity record, your response is more limited and cited articles does not give much information about the history. The major problem in getting the records is not the variation of salinity in oceans (it is not even varying 5ppt globally at current scenario, not worthy to take some small/ medium landlocked lakes/ seas in consideration for longer time scale) but the ice or the ice core (past ice, which is generally being used to know the past) in general, which exclude saline compounds during their formation process from sea water.

Sumanta,

My apologies by going off topic in reply to Dr Towe.

In answer to your question there is a paper here which provides an answer:

Ou, Hsien-Wang. ‘Possible Bounds on the Earth’s Surface Temperature: From the Perspective of a Conceptual Global-Mean Model*’. Journal of Climate 14, no. 13 (July 2001): 2976–88. http://journals.ametsoc.org/doi/pdf/10.1175/1520-0442%282001%29014%3C2976%3APBOTES%3E2.0.CO%3B2   The surface temperature does not continue to rise after the clouds form, and in fact only enough clouds form to stabilise the temperature. This is explained in more detail here: Eschenbach, Willis. ‘THE THUNDERSTORM THERMOSTAT HYPOTHESIS: HOW CLOUDS AND THUNDERSTORMS CONTROL THE EARTH’S TEMPERATURE’. Energy & Environment 21, no. 4 (6 2010): 201–16.

https://www.academia.edu/1097984/The_thunderstorm_thermostat_hypothesis_How_clouds_and_thunderstorms_control_the_Earths_temperature

@ Kenneth Sir, the argument was regarding the capability of living beings for reversal of change when the earth was fully (or at least >70%) covered by the ice (imagine the average temperature then). It is obvious that at that circumstances no direct impact of vegetation / animal life will be there. It was not related to current scenario. The impact of current warming scenario due to living beings is still under doubt ..so as their capability in bringing/driving the long term trend of global changes... as you also rightly mentioned.

I'd like to concentrate on your sub-question, "Which is the initiator of change?" (from Sumanta's original post)  See my article in the new issue of Journal of Hydrometeorology http://journals.ametsoc.org/doi/abs/10.1175/JHM-D-15-0220.1 and preceding articles.  These look at a mistaken assumption that amounts to air temperature being the primary cause of evapotranspiration (ET), and in this case, it leads to extreme overprediction of ET in future warming scenarios.  My short answer is that neither the water cycle nor climate, as summarized by a few variables like near-surface air temperature, precipitation, and wind, is the initiator.  The true initiator is greenhouse gases and their influence on longwave radiation fluxes.  All of the other things that happen are nodes in a complex web of interactions among aspects of the atmosphere and the surface.

Yes, these are possible consequences of global warming. while some are confirmed via series of experimental and simulated evidences, others are still under investigations. It must be cleared too that there are other natural and human activities that have some of the effects stated above .

Hi Kenneth, glad you chose Stykkisholmur on Snaefellsnes. Close to where my mother was born (Rif).

They have records from 1798 and the general trend is warming. Data from the Icelandic Meteorological Office from Stykkisholmur.(fig1)

http://en.vedur.is/climatology/articles/nr/1213

BUT, there is no "hockey-stick" warming trend. There are periods of cooling and periods of warming from 1950-2003 (fig 2.7). Currently Iceland is in a warming period.

Hi Alistair, what about studies showing methane in ice cores correlates to CO2 concentrations?

http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/

http://gcmd.nasa.gov/KeywordSearch/Metadata.do?Portal=amd&KeywordPath=Parameters%7CPALEOCLIMATE%7CICE+CORE+RECORDS%7CMETHANE&EntryId=CDIAC_CH4_LAWDOME&MetadataView=Full&MetadataType=0&lbnode=mdlb3

Kenneth...."records that you pointed to stop at 1999"?? Um... No.

Figure 1 in the link is entitled "Annual temperature in Stykkishólmur 1798 to 2007"

http://en.vedur.is/climatology/articles/nr/1213

You are good at interjecting your spurious points about single year anomalies. Maybe your grandmother would have remembered how interjections from anomalies work out?

Kenneth........"records that you pointed to stop in 1999 (for some reason) so it is difficult to determine what has happened "currently" ...."

Um.. No... I pointed to this record from 1798-2007

http://en.vedur.is/climatology/articles/nr/1213

If you have problems opening links then maybe Microsoft technical services can help you.

Steingrimur,

If you inspect the figure in your link to Ice Core Basics you can see that the concentrations of both CO2 and CH4 have shot up recently. So you could argue that CH4 is causing the current warming. Or you could argue that the rise in CH4 is the result of leaks from oil infrastructure and so is not natural. You could also argue that the rise in CH4 is in ppb as opposed to the rise in CO2 which is in ppm and so the rise in CH4 is insignificant compared to that of CO2. Or you could argue that the rise in CH4 is caused by the greenhouse effect of CO2 warming the tundra. OTOH, you could argue the rise in CH4 is due to warming of the Arctic sea floor by volcanism and is not only entirely natural but is also the real cause of global warming.

But if you apply OCCAM'S razor then global warming is caused by anthropocentric greenhouse gases, and methane is a danger not a cause. See https://youtu.be/iSsPHytEnJM

Here is a picture of the Arctic sea ice today: http://polar.ncep.noaa.gov/seaice/analysis/nh.xml

If Seasons are important for Kenneth then figures 3-6 in Steingrimurs link show temperatures for these up to 2007. Each season show an increasing trend in temperatures. Also 2003 was a hotter year than 1941. Obviously a single year is just weather, while the climate is in the averages (~1.5 °C higher over the period ).

http://en.vedur.is/climatology/articles/nr/1213

Ken,

It is good practice to site your sources so that your fellow scientists can replicate your work. Where did you get that data from?

You have obviously cherry picked your data since it says on this Icelandic Met Office site:: http://en.vedur.is/about-imo/news/nr/3273

"The weather in Iceland 2015:

....

Temperature

The average temperature in Reykjavík was 4.5°C, 0.2°C above the 1961-1990 mean. This is the 20th consecutive year above this mean in Reykjavík. But, it was also the coldest since 2000. In Stykkishólmur the average temperature was 4.1°C, 0.6 above the mean, and 3.8°C in Akureyri, also 0.6°C above the mean."

Ken,

the average annual temperature is 4.1 C but the anomaly is  +0.6 C So the trend up to 2015 is positive not the negative trend you plotted for summer temperatures.

Ken, climate is measured over a thirty year period. Just picking the twelve summers that gives you the result you want is not science. If the average anomaly was zero for the previous thirty years and 2015 was +0.6 then the trend is upwards.

Where are you getting your figures from? You seem to be starting from a very warm year 2003, but we know that 2000 was even colder that 2015. What happens if you start your trend from then? Or if you start 30 years ago - that wont produce a negative trend!

But the main problem is global warming - not about the temperature from a small town on a small island in a small ocean.

Here we are back at the cherry picking discussion. If Kenneth can keep calm and explain the a priori reason to pick 2003 as the starting point. Previously 1998 was a good year to start the analysis that showed the alleged world wide short term cooling trend.

If cooling was ongoing in Stykkishólmur after 2003 should we expect the yearly average temperatures in the following years to be below the climate average or the long term (increasing) trend line from figure 1 in Steingrimurs link? They appear all to be above! During Kenneths alleged cooling period 2010 was the 2nd warmest year ever recorded (in a more than 200 years dataset) and the second latest year in the series, 2014, appears to be the 3rd warmest in 200 years.

Kenneth writes "how can anyone pick the result they want...in advance?" This is the core of the cherry picking problem versus scientific data treatment. In science one doesn't want something - the data treatment should be selected before considering the actual numbers.

https://en.wikipedia.org/wiki/Cherry_picking#In_science

http://www.ibtimes.co.uk/debunking-climate-change-hiatus-there-was-never-slowdown-global-warming-1520118

Article Climate-change ‘hiatus’ disappears with new data

• Ashkans source is the link in the beginning of the post with the graphs.
• I do see temperatures on Ashkans graphs (°F on hight axis, °C on left).
• The data is for 1980-2015, but the trend is calculated with all the data back to 1880.

There is an explanation in a link from the page the data are found in. I don't feel responsible for for explaining this. As I read this it seems the NOAA decided that the anomalies are a better measure for the temperature development, so for each dataset the anomaly is relative to the 1981-2010 base period. They appear not to want to give a global average temperature.

What can one learn from comparing the average temperature in the US with the Northern Hemisphere LAND temperature?

http://www.ncdc.noaa.gov/monitoring-references/faq/anomalies.php

An Interesting link relevant to the original topic of discussion:

https://www.ncdc.noaa.gov/data-access/paleoclimatology-data/education-outreach (Click Introduction to Paleoclimatology)

Major points are...

Introductory Paleoclimatology

Why Should We Care About Climate Change?

How Do Scientists Study Past Climates?

What Do We Know About the History of Climate?

About Paleo Proxy Data

What is Glaciation? What Causes it?

What is The Milankovitch Theory?

More Importantly, What does The Milankovitch Theory say about future climate change?

https://www.ncdc.noaa.gov/data-access/paleoclimatology-data/education-outreach

For Global and Regional Analysis of significant events of (1) Climate, (2) Hazards, (3) Snow & Ice, (4) Upper Air, and (5) ENSO .....during late 1990s to till date following webpage also gives useful information:

http://www.ncdc.noaa.gov/sotc/ 

for example see the images about Significant Global Climate Events (Image/Map Credit NOAA-NCDC & WMO) for year 2009, 2010, 2011, 2012, 2013, 2014, and 2015...

http://www.ncdc.noaa.gov/sotc/

Alistair,

If you inspect the figure in my link to Ice Core Basics. http://www.antarcticglaciers.org/glaciers-and-climate/ice-cores/ice-core-basics/

You can see that both CO2 and CH4 concentrations and temperature spike together. All well before humans began exploiting oil on a massive scale.

Plus, CH4 is ~20X more potent greenhouse gas than CO2.

http://climatechangeconnection.org/emissions/co2-equivalents/

But back to my initial question: For the past ~500.000 years CO2 has gone up and down, CH4 has gone up and down, temperature has gone up and down.

Based on this, what is the evidence that the recent warming (~200 years) is only due to human activity and not other natural causes? 

In both Kenneths' graphs it is the HadCRUT4 data that appear to pause.

If one considers the most current graph the trend appears to be back to the steady increase since about 1980.

https://crudata.uea.ac.uk/cru/data/temperature/HadCRUT4.pdf

Steingrimur. Thought CH4 is more potent than CO2 it's concentration is 200 times lower in the atmosphere. N2O + CH4 are important part of the increased greenhouse effect, but in the order of 15-20 %.

For me the parameter "Increased radiative forcing (W/m2)" of each gas shown in the table in the link explains the relative importance of the increase in gasses.

https://en.wikipedia.org/wiki/Greenhouse_gas#Natural_and_anthropogenic_sources

Hi Henrik, thanks for the clarification and link.

But I am still wondering how the current warming trend is ascribed to human activity whereas ancient warming trends are ascribed to natural causes.

What distinguishes them?

Steingrimur,

Are you saying that because CH4 went up and down in the past and no-one is saying mankind is driving the methane, therefore global warming could be caused by methane and it is not the fault of mankind?

We know that we have increased the CO2 content of the atmosphere because we have estimated the amount of fossil fuels we have burnt and the amount of CO2 they would have produced. Only ~60% is in the atmosphere and the remainder is in the oceans causing acidification there which is likely to destroy shell fish.

We also know that CO2 caused global warming and when the tropics and tundra warm they give off methane. So the increase in methane is an indirect effect of fossil fuel burning. And the rise in CH4 now is also a result of the increase in CO2. Why else is CH4 rising?

Also CH4 is 25 times as powerful as CO2 but the concentration of CO2 is 400 ppm and CH4 is 1800 ppb = 1.8 ppm. So even multiplying it by 20, CH4 has the samee effect as 36 ppm of CO2.

Henrick,

Here are the NOAA graphs and they do not show the hiatus that Ken is insisting on:

http://data.giss.nasa.gov/gistemp/graphs_v3/

Steingrimur,

Presumably you are now wondering where the CO2 came from during the previous cycles if it was not from burning fossil fuels. I'll let you into a secret - nobody knows!

Alastair,

That is exactly what I was wondering about. Thanks.

I cannot answer to why Kenneth have these theories about my intentions and goals that I have never expressed. Perhaps he is just trying to make a strawman.

The different curves of temperatures do not show a decreased if the most recent years are included. That you can mathematically calculate a decreased slope between years in a limited interval 1998-2010/2013 became meaningless as 2014 and 2015 was so clearly hotter bringing the trend back to the same increase.

https://en.wikipedia.org/wiki/Straw_man

I've taken a glance at this discussion after being absent for a while, and saw there was a response from Kenneth, questioning my statement about greenhouse gas concentrations being the true initiator.  I'll admit that this assumes the conventional position of human-emitted GHGs causing warming.  I haven't read or absorbed all of the many arguments posted here, and don't have much to say about them.  My central point, getting back to Sumanta's original question of whether climate or water cycle is the initiator, is that neither is the initiator, and you have to look at the driving mechanism behind climate to understand the relationship between things like air temperature and evapotranspiration.  If you think of "climate change" in terms of simply the difference between winter and summer, the primary driver is the amount of solar radiation impinging on a given point on Earth in a given season, which has its influences on air temperature and water cycle.  If you think in terms of Milankovitch cycle, the primary driver might be the correspondence between seasons and Earth's perihelion, interacting with feedbacks involving greenhouse gases, sequestering of water in continental glaciers, and many more complicating factors, all again having some influence on air temperature and water cycle.  There is no single arrow of causality from climate (poorly defined in the original question) to water cycle, or in reverse.  The paper I cited criticizes a hydrologic model that has been repeatedly used for climate change impact assessment, because it has an a priori assumption that air temperature is the primary predictor of evapotranspiration, regardless of the driver behind the air temperature's variability and change.  This model was calibrated during a period when the main mode of variability was the seasonal cycle, but tries to extend this relation to scenarios of change due to increased GHGs, with disastrous results.

All,

Thanks a lot for sharing your views/opinions/responses and for the active participation towards a common objective i.e., to understand the dynamics and complexity of earth's climate and associated things.

@Brent sir, I have only framed an unidirectional outline in my formulation (as given in the question) considering major physical changes as perceived by a layman. I know there are many more things that need to be considered to frame the formulation of such a complex interaction.

However, all of you must have faced similar problem while writing question @RG. I was unable to prepare a chain of climate and water cycle dynamics with multiple entry (in) and exit (out) points of variables as generally been done in charts/graphs. But, I assure you all that I will summarize the outcome and will prepare a chart of similar type after getting a few more satisfactory and relevant answer of my original question....i.e, how the complex dynamics are being maintained for seasons after seasons... years after years ... since its inception at very early stage? 

Till date, after reading all responses posted here along with visiting relevant webpages plus analyzing a few critical points that was running in my mind, ...my view about the trigger of change or the cause of reversal of direction of change (of dynamics between the two) and the flow and mechanism of persistent complex dynamic equilibrium would be like as follows:

"The earth has experienced many ice ages and warming phases in the history only because the correlation between the two had never been static ...as mentioned earlier it might be dynamically seasonal but not a true seasonal either. The true shape or real picture of the earth at any given time is basically determined by the prevailing circumstances of dominance of elements (may be in gas, liquid, solid or in mixed form) that was active (operational) at that time. Each and every element has had their unique role to play either as an independent or as a complex chemical form...not necessarily only the green house or neutral gases that we know today. The variability of composition of gases in the earth's atmosphere at every moment/age/phase determine its elasticity and naturally design its extremities. When climate-water cycle reach that natural extreme stage they start to retreat to form the basis of the dynamic equilibrium. Once they start reversal they keep moving more unidirectionally towards reversed direction, which leads to change in the composition of elements (reforming and regrouping and so on) which again bring the apparent changes or look of our physical earth (including the biological and chemical changes), until they face another elasticity barrier of extremity. The elasticity capacity/range is also not fixed and keep changing each and every change it experiences in each and every second of changing time....that is why the strength and duration of past ice ages are not same. Furthermore, because of non-linearity of interaction dynamics of elements in action the earth has had to face intermittent pause/ shocks but major trend (of global change between two extreme of prevailing elemental elasticity) has been maintained."

I would appreciate all of your's responses/criticism on my conceptualization as it stand now with justifiable arguments.

@Kenneth sir, here major trend means i wanted to say that the primary non linier unidirectional trend between extreame/peak ice age to peak global warming and vice versa. And its dynamic balance (everchanging corelation between climate and water cycle) with the prevailing elements ensure the major direction of change untill it reaches to either extreme.

Dear Sumanta, I do not know what has driven you for such summary (post # 80). Maybe you are writing project proposal or report. It looks good that we have managed to bring together many ideas from different sources, often contradictory. I guess that the group of discussants here has mainly physical background in education (I have also an economic apart from that), and that is why some weak consensus is possible in principle. But if economists and policy makers would enter our discussion now, I think that we will stay even further from the consensus point.

It is also important to know why this consensus is required. The problem is clearly interdisciplinary, and perhaps nobody of us has all knowledge from different branches of science relevant for it. I also think (as I have stressed in my post in the beginning) that we have to react today, even before we have the full knowledge. Because the problem is not only academic – it is the threat. Animals in the past were simply unable to understand and confront this process, and had only to adapt. Some of them perhaps did not survive those climate changes.

It may be not so important to know all complex interlinks between different processes (change of water level, temperature, concentration of different gases) in the past in all details. It is important to forecast what will happen in the next 100 years with us. There are definitely many nonlinear and hysteresis phenomena, so that 30% increase in CO2 may mean just 30 cm increase in ocean level in the past century, but maybe 10 meters in the next one. If such model will be created, it is less important that it explains all past but it is crucial how it works for present trends and how far it is from future events. Clearly, nobody will know exactly (and tell) before it happens – but this is a natural objective. I think that the interview with Bryson cited by Kenneth has a similar argument.

I also want to attract your attention to another practical question that also has both physical and economic components:  https://www.researchgate.net/post/What_will_come_first-non-acceptable_global_warming_or_extinction_of_oil_reserves .  Your opinions are welcome.

Yuri Sir and Kenneth Sir,

Both of you seems having different perspective and entirely contrary point of view to look into the future climate change scenario... However, have one thing in common that is get ready (be prepared) for adaptation to the climate (nature).

Views also blended...Kenneth sir's towards natural selection and its careful adaptation and Yuri sir's towards possibilistic approach of determination.

And, regarding..

"this research indicates that the interval from the end of one glacial epoch to the beginning of the next averages out to be around 10,000 years, plus or minus a thousand years"

.... I am unable to digest this in my mind at this stage may be because of my limitation of knowledge in this field. Whatever little I read about dating of fossils and rocks and their past records ...will straightway reject such hypothesis. If it is about micro changes like stock market fluctuation on daily basis, then I have nothing to comment.

I would like to refer a few things in addition to the earlier ones. see below:

https://judithcurry.com/2016/01/22/history-and-the-limits-of-of-the-climate-consensus/

http://www.oarval.org/ClimateChangeBW.htm

http://www.stateofourclimate.com/

...as the graphs posted there (pls. visit the webpages for details, and see the references there for image credits) will make reader think twice about the phase that we are in. However, it is evident from the graphs and past literature that.... from here on if more global warming will happen it has to happen very fast or if the long term coiling persist it will be slow. But, certainly we are near to the flag end of the elasticity barrier (in terms of long term past records, if they are true) of long term trend.

pls. keep in mind the different plate's tectonic movement (with its direction and speed) in the earth's crust, the convection current of upper mantle and asthenosphere, and also the location of continents and oceans that we see today in true sense while interpreting ice core data based past records about global climate otherwise all these record has nothing to explain.

https://judithcurry.com/2016/01/22/history-and-the-limits-of-of-the-climate-consensus/

http://www.oarval.org/ClimateChangeBW.htm

http://www.stateofourclimate.com/

Out of curiosity, I looked at the entry you point to from the Judith Curry blog, which is mostly quoting an essay by historian Philip Jenkins.  While it brings up some points that are true and worthy of consideration, other aspects of it are twisting science's understanding of historical climate.  I am not an expert on the Little Ice Age, which Jenkins claimed involved a 2oC drop in temperature that was global in scope.  In particular, I had understood that it was largely limited to the region surrounding the North Atlantic.  I went to Wikipedia, which had this quote from the IPCC 3rd Assessment:

"Evidence from mountain glaciers does suggest increased glaciation in a number of widely spread regions outside Europe prior to the twentieth century, including Alaska, New Zealand and Patagonia. However, the timing of maximum glacial advances in these regions differs considerably, suggesting that they may represent largely independent regional climate changes, not a globally-synchronous increased glaciation. Thus current evidence does not support globally synchronous periods of anomalous cold or warmth over this interval, and the conventional terms of "Little Ice Age" and "Medieval Warm Period" appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries... [Viewed] hemispherically, the "Little Ice Age" can only be considered as a modest cooling of the Northern Hemisphere during this period of less than 1°C relative to late twentieth century levels.[10]"

He also treats human-caused warming and natural climate variability as an either-or choice, not both-and.  There have been natural variations in the past, yes, but science has brought forward the idea of another forcing that has risen in magnitude over the last two centuries and perhaps especially the last half-century.  This then coexists with the ongoing natural variability.  So the question that needs to be asked is, "How significant is this forcing from human-emitted greenhouse gases compared to natural variability?"  Jenkins does not address this question, but tries to argue that because invoking GHGs alone doesn't explain why there was a slowdown in warming between the then-warmest year in the instrumental record by a large margin (1998) and 2013 or so, then invoking GHGs at all lacks predictive value at the century time scale.  I.e. you can't claim that human causes and natural variability exist side by side and act simultaneously--trying to force a choice that is unnecessary and false, but is trotted out almost without fail in public discourse on climate change.

Something that might seem more nitpicky to non-experts, but both key and problematic in Jenkins's argument, is his claim that air temperatures should be correlated with greenhouse gas emissions, as distinct from GHG concentrations--concentrations being the actual driver of the greenhouse effect, and being due to an accumulation of emissions.  Think about asking, "How much does a (possibly slightly leaky) bathtub weigh when it has water pouring into it?"  Would you expect the rate of flow into the tub to be the sole predictor of its weight at a given time?  If you start water flowing at 0 minutes, then cut back the flow to 1/10th of its original rate at 5 minutes, would you be surprised that the weight at 5.5 minutes is greater than at 1 minute?

Much of the discourse in this thread has had difficulty with the cumulative aspect of anthropogenic greenhouse warming--in addition to the relation between emissions and concentrations just mentioned, the lag in global air temperatures due to the thermal capacity of the oceans, and the necessity of ocean water to gradually cycle to the surface, warm, and undergo thermal expansion in order to actuate sea level rise.  If the GHGs are only temporary, then no worries about cumulative effects, but if they stick around for a while (hint: they will), then watch for effects to accumulate, with possible breaks in some effects for a time because natural variability still exists.

The earth climate dynamics  simply maintain its equilibrium by the law of physics and chemistry: The systems normally move towards the lowest energetic state, heat moves from warmer to colder regions, energy is dispersed, and equilibrium is achieved (or at least approached).

What I meant was just thinking in terms of signal vs. noise.  If we take global mean surface air temperature in particular, there is a natural variability to it that may be considered "noise", while temperature change due to anthropogenic greenhouse gases could be considered the signal.  So I'm saying the question is, how do they compare?  And the consensus viewpoint, with which I agree, is that the signal is now overtaking the noise and will continue to grow.

Something like El Nino, as Glantz addresses, is a question of a different order--a trend in variability, not in a mean quantity.  El Nino is a mode of variability and begs the question, is this mode of variability increasing in magnitude?  My impression is that this proposition is on rather shaky ground in terms of matching theory and observation.

Dear Sumanta, you have added a set of interesting pictures. Note that a lot was different millions years ago, including shapes of continents. We do not know if the total mass of water in the ocean and atmosphere was then the same as today and what share of it was in the form of ice. Moreover, for different shapes of continents melting of the same amount of ice would mean different change in the ocean level.

I do not know if we could trust all of them, but definitely most of economists working on climate change are not aware of them. Many of them believe that the knowledge of physicists about climate change is so exact that we need to extract (let say) not more than 30% of available resources of fossil fuels cumulatively if we want the temperature increase to stay below (let say) +2 degrees C.

It is indeed important to work on better climate models. Brent Lofgren is right saying that we need to consider both stocks and flows. Even if we will manage to stabilize temperature growth by 2 degrees (for physicists – let us assume that anthropogenic component of climate change dominates), not all effects will come immediately. We do not know what is the long term equilibrium level of the ocean at this level of temperature. It may well happen that (like in “Titanic” movie, when a part of the ship half-broken in 2 parts kept on the surface, while the 2nd part went deeper and later has moved it too) short term effect will be equilibration, but ocean level will rise steadily reaching non-acceptable (for us, not dinosaurs) levels of +10 meters, for example.

In complexity science two types of variables are introduced – fast and slow. These slow variables are really governing long term dynamics. There are also many threshold phenomena, and we do not know all of them (for our climate change science).

Kenneth, I think that removing 20% CO2 from the atmosphere was never an economic plan. The best suggested thing was to stabilize emissions (flow), then to reduce it to maybe 50% of the current – and to hope that the stock will not increase fast enough in order for temperature to stabilize.

Suppose that we are now on natural period of temperature increase – and we expect  peak to be, let say, +N degrees (N=3, 4,5,…) . Given our burning of fossil fuels, we can shift this peak to N+M, where M=2,3,4 degrees and is usually determined in climate change scenario models based on CO2 emission dynamics.

Some economists also believe that a substantial fraction of CO2 will dissipate from atmosphere to the ocean in about 100-200 years, and then slowly convert to coal. I  guess that this process in much slower. Do you know the correct time scale of this process?

I think we should not initiate another set of 'Earth Engineering' by way of artificial removal of CO2 from atmosphere. Though the climatologists are more concerned about present all time high world temperature being observed during summer at many places, but we should not forget that the so called all time high is based on documented instrumental record of temperature of less than 250 years only. Most importantly, we (humans of modern civilization) are here in this earth for less than a second of a day (24hr) of earth's overall time span. Atmospheric CO2 is not at all time high (very close to all time low in long term perspectives)....so is the climate extremities ...there is a lot more in store, waiting to come to reshape the so called anthropogenic era.

We did many set of Earth Engineering in recent past; starting from Industrialization, Urbanization, Engineering of radioactive elements, Medical revolution ....to most recent Technological Revolution for the sake of comfort and to show off our dominating nature. But, probably we have still not faced the 'Equal and opposite reaction from the opposite side'. Or may be we have almost done...used up most if not all, resources and now afraid to face the reaction from the other side.

Many thinkers of scientific community are self-realizing of the wrong doing and want to undo a few things which they think can be done with out affecting the larger ecosystem. Now again, as like we did in past we are thinking that we will be doing the reverse engineering for the betterment of the earth but possibly (and unfortunately) we are not. We will again be defeated by ourselves only. Only time and god (if the one really exists, Note: I am a believer) knows.

I hope I am able to convey my doubts and assessment of the topic with every response I posted till now (I often question my articulation capability). Thanks to yours overwhelming response, the thread will soon touch 99+ response within 20 days of first post (a rare phenomenon for scientific topic in research gate). And yeah, I forgot to mention, the Noise and Signal concept as exemplified by Brent sir is good one (as like the visualization from movie titanic by Yuri sir) for practical understanding. Thanks.

As for the original question on the water cycle:

the questioner should read/study the IPCC AR4 report

Frequently Asked Questions FAQ 8.1 | How Important Is Water Vapour to Climate Change?

http://www.climatechange2013.org/images/report/WG1AR5_Chapter08_FINAL.pdf

starting at page 666

@Harry ten Brink,

Thank you sir for the link. I have read it (part of the report). It is quite interesting and resourceful.

Sumanta

I am rather surprised / dispappointed

The IPCC report of working group 1 is the encyclopedia of Climate Change and not just "interesting". It summarises the thousands of publications and is written by (the) leading  climatologists of a host of countries. Beats all else with respect to climate science