What causes climate change and global warming?
This question has been debated a lot, because climate change can be “due to natural variability or as a result of human activity” (IPCC 2007) and because the climate system is very complex.
There is new and stronger evidence that most of the warming over the last 50 years is due to human activities. Ice cores taken from deep in ancient ice of Antarctica show that carbon dioxide levels are higher now than at any time in the past 650,000 years. More carbon dioxide in the atmosphere means warming temperatures. In its 2007 report to the United Nations, the Intergovernmental Panel on Climate Change (IPCC) concluded that it is more than 90 percent likely that the accelerated warming of the past 50-60 years is due to human contributions.
These contributions include increased levels of “heat-trapping” gases (a.k.a. “greenhouse gases”) such as carbon dioxide in the Earth’s atmosphere. One of the biggest ways people contribute to greenhouse gases is by burning fossil fuels. We use coal, oil, and natural gas to generate electricity, heat our homes, power our factories, and run our cars.
Changing land use patterns contribute, too. Trees and other plants use carbon dioxide and give off oxygen. When trees are cut down for development, agriculture, and other purposes, they’re no longer available to take carbon dioxide out of the air, and actually release carbon dioxide as they decay or burn.
As the levels of carbon dioxide and other greenhouse gases increase, more heat is “trapped” and global temperatures rise. This causes significant changes in the timing and length of the seasons as well as the amount and frequency of precipitation. (IPCC 2007)
Intergovernmental Panel on Climate Change – Climate Change 2007: The Physical Science Basis, Summary for Policy Makers; 2007
Date: 2015-04-20; view: 173