Chemical weathering over the geological long term acts to remove CO2 from the atmosphere. Schaefer et al. Water vapor is another greenhouse gas and further increases the warming. [81] The Antarctic sea ice reached its greatest extent on record since the beginning of observation in 1979,[82] but the gain in ice in the south is exceeded by the loss in the north. The result is a much larger greenhouse effect than that due to CO2 alone. They also claim that there is much more to discover about the issue in Antarctica[38] Quart of the marine methane is found in the region of Antarctica[39], Literature assessments by the Intergovernmental Panel on Climate Change (IPCC) and the US Climate Change Science Program (CCSP) have considered the possibility of future projected climate change leading to a rapid increase in atmospheric methane. The term "forcing" means a change which may "push" the climate system in the direction of warming or cooling. On the other hand, evidence from paleoclimate variations indicates that climate sensitivity could be higher than the above range, although perhaps only on longer time scales. Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text. For the fact-checking website, see, Last edited on 13 September 2020, at 04:10, Scientists warn thawing Siberia may trigger global meltdown, "Climate Science Special Report / Fourth National Climate Assessment (NCA4), Volume I", "The Study of Earth as an Integrated System", "Climate tipping points — too risky to bet against", "8.6.3.1 Water Vapour and Lapse Rate - AR4 WGI Chapter 8: Climate Models and their Evaluation", "Climate Change 2007: Synthesis Report. ACS Professional Education
These effects of clouds are examples of negative feedbacks in the climate system. If models incorrectly project future changes in the carbon cycle, then concentration or temperature targets could be missed. [90], Net primary productivity changes in response to increased CO2, as plants photosynthesis increased in response to increasing concentrations. Which of the following are examples of positive feedback? In September 2007, the Arctic sea ice area reached about half the size of the average summer minimum area between 1979 and 2000. Network with colleagues and access the latest research in your field. It is also possible that climate could undergo a sudden large change in response to accumulated climate forcing. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Do you enjoy reading reports from the Academies online for free? Some initial change causes a secondary change that reduces the effect of the initial change. In particular, the magnitude and even the sign of the feedback can differ according to the composition, thickness, and altitude of the clouds, and some studies have suggested a lesser climate sensitivity.