Sunday, February 1, 2009

IPCC: Summary for Policymakers. In: Climate Change

In the report of Working Group I of the Intergovernmental Panel on Climate Change (IPCC), advancements have been made about how both human and nature affect climate change. Since the Third Assessment Report (TAR), there have been significant improvements in understanding climate change. By better understanding models and further complex data analysis, we can better comprehend climate change and better predict future patterns.
There have been significant changes in the atmosphere due to greenhouse gases and aerosols, for example, that have made it difficult to balance our climate system. Because society is so reliant on fossil fuels, there has been a global increase in carbon dioxide, methane, and nitrous oxide concentrations. Carbon dioxide concentrations have increased from 280 ppm to 379 ppm since pre-Industrial Revolution era to 2005. More than 1/3 of nitrous oxide emissions are anthropogenic (caused by humans) due to agriculture. Overall, human activity has consequently created a warming global average since 1750.

With efficient balloon-borne data, satellite data, and improved ground based measurements, we can clearly observe the increases in global average air and ocean temperatures, melting ice, and sea levels. In fact, eleven of the past twelve years have been some of the warmest years on record as far as surface temperatures. Since the 1960’s, warmer temperatures have caused ocean depths to reach 3000 meters at a rate of approximately 3.1 mm per year between 1993 to 2003. Mountain glaciers and snow cover amounts have also decreased. Frozen ground in the Northern Hemisphere has declined by 7% in the last one hundred years.

Climate change has also resulted in altered precipitation amounts, ocean salinity, wind patterns, droughts, heat waves, and more intense tropical storms. More precipitation has been observed in South America and Europe while dryer patterns were found in the Mediterranean and southern Asia. Precipitation and evaporation over the oceans have increased salinity in lower latitude regions.

Palaeoclimatic studies gather past climate changes from decades to millions of years ago in order to help explain other global patterns. An example the article uses is tree ring width. Local factors, such as precipitation amounts, may influence data results and must be taken into consideration. Therefore, results are not necessarily 100% accurate and may result in uncertain estimates in climate changes. However, these studies do increase the confidence in understanding our climate system. Palaeoclimatic information has shown the global warming patterns have been abnormal in the last 1,300 years. Warming of the troposphere and cooling of the stratosphere is likely due to greenhouse gas increases and ozone depletion. Humankind is likely to be a cause for changes in wind patterns that affect the more intense tropical storms we have seen in the past decade as well as the increase in heat waves. Water vapor changes also provide the largest feedback affecting the climate.

Future climate change may be better predicted with more models and additional observations. Thus far, it is predicted the next 20 years will result in an increase of 0.2 degrees Celsius in regards to greenhouse gas emissions and aerosols. Even if these levels were held constant, the overall temperature will still rise due to the slower response of the oceans. If they continue to increase as predicted, this could affect acidity levels in the oceans. Most of the predicted warming is expected in the Northern Hemisphere. Thaw depths are also expected to increase and oceanic ice is expected to shrink. Heat waves, heavy precipitation, and tropical storms may become more frequent and more intense. Interestingly, the Antarctic Ice Sheet will stay too cold for melting.

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