The United Nations released a major report last week, finding with more certainty than ever before that humans, chiefly through the burning of coal, oil, and natural gas, are a key cause of the Earth's warmer temperature.
"It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century," states the report, issued by the U.N. Intergovernmental Panel on Climate Change. The report, which was written with input from 600 authors from 32 countries, is 95 percent certain of humans' involvement. This is up from the 90 percent certainty it reported in 2007.
The report did provide less certainty about how global warming will affect different parts of the world via extreme weather like droughts, heat waves, and the like. It also sought to explain why the global temperature hasn't risen as rapidly in recent years, saying that much of the heat is being soaked up by the oceans and is a temporary phenomenon.
The report endorsed what's called a "carbon budget"—the amount of carbon that can be emitted to avoid the most dangerous aspects of a warmer planet. The upper limit is 1 trillion tons. About half of that has been emitted already since the 1950s, and if we continue as business as usual, we'll reach that upper limit by 2040, according to The New York Times. The Times also reported that more than 3 trillion tons worth of carbon is still in the ground stored within fossil fuels.
"Continued emissions of greenhouse gases will cause further warming and changes in all components of the climate system," the report states. "Limiting climate change will require substantial and sustained reductions of greenhouse-gas emissions."
Still, the report it admitted that even if everyone stopped burning fossil fuels tomorrow, much of the climate damage has already been done, illustrating the grand difficulty of this global problem. "Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped," states the report. "This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2."
What does this report say about the scope of the global-warming problem? How can countries prioritize this serious challenge as they also face other, more imminently threatening, problems, such as poverty, disease, national security and economic woes?
What role can the United States play in leading the way on a comprehensive, international approach to addressing global warming? Does the action by the Environmental Protection Agency to regulate greenhouse-gas emissions from power plants help put the United States in more of a leadership position? And could it prompt similar action by other countries?