1.Multiple temperature records from all over the world have all shown a warming trend, and these records have been deemed reliable by the National Aeronautics and Space Administration (NASA), and the National Oceanic and Atmospheric Administration (NOAA), among others (EPA, 2011). Other observations that point to higher global temperature includes: warmer oceans, melting arctic sea ice and glaciers, sea level rise, increasing precipitation, and changing wind patterns (EPA, 2010)
2.There were times in the distant past when Earth was warmer than it is now. However, human societies have developed and thrived during the relatively stable climate that has existed since the last ice age. Due to excess carbon dioxide pollution, the climate is no longer stable and is instead projected to change faster than at any other time in human history. This rapid climate change will expose people to serious risks. Sea level rise, increasing droughts and wildfires in some regions and increasing flooding in others, more heat waves, and other effects of climate change all pose risks to human health, infrastructure critical to our homes, roads, and cities, and the ecosystems that support us (USGCRP (2009).
3.Plants, oceans, and soils release and absorb large quantities of carbon dioxide as a part of the Earth's natural carbon cycle. These natural emissions and absorptions of carbon dioxide on average balance out over time. However, the carbon dioxide from human activities is not part of this natural balance. Ice core measurements reveal that carbon dioxide levels in the atmosphere are higher than they have been for at least 800,000 years (USGCRP, 2009). The global warming that has been observed in recent decades was caused by elevated levels of carbon dioxide and other greenhouse gases in the atmosphere, due primarily to human activities (NRC, 2011)
4.A few extra cold or snowy winters in your hometown doesn't mean that global warming isn't happening. We know that global average temperatures are rising. However, even with this global warming, at the local or regional level, we can expect to have some colder-than-average seasons or even colder-than-average years. For example, in the Eastern United States, the winters of 2010 and 2011 were colder than the average winters from the previous decades. In fact, extra snowy winters can be expected. In a warmer climate, more water vapor is held in the atmosphere causing more intense rain and snow storms. As the climate warms, we do expect the duration of the snow season to decrease — however, as long as it is still cold enough to snow, a warming climate can lead to bigger snowstorms (USGCRP (2009).
5.Changing the average global temperature by even a degree or two can lead to serious consequences around the globe. For about every 2°F of warming, we can expect to see
5—15% reductions in the yields of crops as currently grown
3—10% increases in the amount of rain falling during the heaviest precipitation events, which can increase flooding risks
5—10% decreases in stream flow in some river basins,
200%—400% increases in the area burned by wildfire (NRC, 2011).
Global average temperatures have increased more than 1.4 degrees Fahrenheit over the last 100 years (NRC, 2010). Many of the extreme precipitation and heat events that we have seen in recent years are consistent with what we would expect given this amount of warming (USGCRP (2009). Scientists project that Earth's average temperatures will rise between 2 and 12 degrees Fahrenheit by 2100 (NRC, 2011)
References
1.NRC (2011). America's Climate Choices: Final Report . National Research Council. The National Academies Press, Washington, DC, USA.
2.NRC (2010). Advancing the Science of Climate Change . National Research Council. The National Academies Press, Washington, DC, USA.
3.NOAA (2011). 2010 Tied For Warmest Year on Record . National Oceanic and Atmospheric Administration. Accessed 3/16/2012.
4.EPA (2010). Climate Change Indicators in the United States . U.S. Environmental Protection Agency, Washington, DC, USA.
5.USGCRP (2009). Global Climate Change Impacts in the United States . Thomas R. Karl, Jerry M. Melillo, and Thomas C. Peterson (eds.). United States Global Change Research Program. Cambridge University Press, New York, NY, USA.
6.NRC (2011). Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia . National Research Council. The National Academies Press, Washington, DC, USA.
7.IPCC (2007). Climate Change 2007: Synthesis Report .Contribution of Working Groups I, II and III to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change [Pachauri, R.K. and A. Reisinger (eds.)]. Geneva, Switzerland.
8.EPA (2011). Endangerment and Cause or Contribute Findings for Greenhouse Gases under Section 202(a) of the Clean Air Act, EPA Response to Public Comments. U.S. Environmental Protection Agency. Accessed 3/16/2012.
