The common thinking is that the globe is warming. It is very obvious that the warming would affect both the continents and oceans. In fact there is evidence that ocean waters are getting warmer. In consequence, I wonder about the following chain of possibilities.
1. If the oceans get warmer, there should be more evaporation.
2. More evaporation should lead to more vapors in the atmosphere (and also clouds and rainfall).
3. More vapors and clouds should reflect back some of the suns radiation.
(Please note I am not pleading that global warming is a bless. It is already getting too late to control the damage of the existing and regularly added, CO2 to the atmosphere).
You have arisen a very good point to think about. We know that on an average cloud deals with 52 units (out of 100 u),. absorbs 10 U, transmits 17 U to the ground and reflects back 25 U.in the Northern Hemisphere (Gates 1962). If the cloud cover increased, the proportion might be changed, the amount of incident radiation may be reflected back more. That will reduce the radiation!!! But some more factors are involved and it depends upon solar angle, upon absorption and scattering coefficients which are complex functions of wavelength and upon the depth, density, composition and temperatures of the atmosphere (Bannister 1980). Increased water vapour will absorb and hence will send back more heat to the earth causing more global warming!!!
As noted by Ashfaque Ahmed, this is a complex problem, and one that -- from what I understand -- is difficult to predict because of the potential variations. NASA has a nice summary of these issues from its international satellite cloud climatology project :
http://isccp.giss.nasa.gov/role.html
A very interesting question. However, I am of the opinion that this is climate restoration because similar changes have been reported in the history. These are ecological processes that change and restore.
Hi, Qasim. Warming of the atmosphere and Earth surface leads to several important changes.
• Reduced sea-ice thickness and extent in the arctic during the summer.
• Increased melting of glacial ice on continental crust, including those in Greenland, Antarctica, and our beloved Karakoram.
• Rising sea level due to increased volume of water in the ocean basins from melting glaciers and thermal expansion of water, which increases the "dark" surface area of Earth (the oceans) at the expense of the lighter continental areas above sea level.
• Increase in cloud cover due to evaporation, along with a variety of potential weather effects.
• Changes in the location and perhaps extent of deserts, as well as changes in the location and perhaps extent of vegetated areas.
• Soil loss due to deforestation.
• Habitat loss and associated reduction in biodiversity.
These changes will be very challenging to future generations. Sea-level rise will inundate enough land surface that large-scale resettlement of people who currently reside within a few meters of sea level is inevitable, including people currently living in coastal communities (large and small) and some entire island nations. Availability of potable water, food, healthcare, natural resources, and energy will continue to be a significant challenge as more people share less land. (Earth's population in my lifetime has increased by about 2.5x so far.)
Global warming is a problem that will require coordinated responses that are global in scope if we are going to change the factors that are within our ability to change. Yet we must have the intelligence and courage to make those changes, and the foresight to understand that we do so as an act of love for our children's grandchildren and countless others we will never know. Indifference and inactivity now will likely have disastrous consequences later.
Held, Isaac M., and Brian J. Soden. 2000. ‘Water Vapor Feedback and Global Warming’. Annual Review of Energy and the Environment 25 (1): 441–75. doi:10.1146/annurev.energy.25.1.441.
Dear Dr Jan,
In general you are correct, that an increase in temperature will increase humidity and clouds. However, water vapour is a greenhouse gas, and clouds also act to increase the greenhouse effect. So, although increased clouds would reduce the effects of solar radiation at the top of the atmsophere, they would also increase the temperature at the surface.
It is believed that on Venus the greenhouse effect of water vapour increased the surface temperature causing a runaway warming until the carbonate rocks released CO2 which continued the runaway. Eventually the surface temperature reached the melting point of lead. It is argued that woudl not happen on Earth, since if it was possible it would have happened already.
1. Clouds reflect some of the incoming sunlight back into space. So, it cools the Earth.
2. Clouds warm the Earth by absorbing infrared radiation emitted from the surface and re-radiating it back down. The process traps heat like a blanket and slows the rate at which the surface can cool. So, it warms the Earth’s surface.
3. But the amount of cooling effect produced due to reflecting back of the solar radiation into space is more than the amount of heating effect produced due to blanketing effect.
4. Thus, the net effect of clouds on the climate is to cool the surface.
The cause and effect of global warming is global and it is complex and difficult to predict unilaterally. The solar radiation cannot be surely handled only by the phenomenon of global warming.
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