Is there disagreement among scientists about climate change? Is it caused by humans?


The US National Academy of Sciences has declared that climate change is occurring and that humans are very likely causing it. So have the scientific societies of China, France, Germany, India, Japan, Russia, Brazil, the United Kingdom, and many other countries.

The Intergovernmental Panel on Climate Change, or IPCC, a body made up of hundreds of experts from scores of countries, issued their most recent report, the Fourth Assessment Report, in 2007, saying that “warming of the climate system is unequivocal.” The IPCC periodically assembles peer-reviewed research on climate science into an overall picture. Representatives from member countries, including the US, negotiate the wording of the final report line by line. The most recent report says, “Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic GHG [human greenhouse gas] concentrations.”

More recently, in June 2009, the US Global Change Research Program, which is a joint scientific venture of 13 federal agencies and the White House, released the results of a multiyear study. This study, like many others, found that “the global warming observed over the past 50 years is due primarily to human-induced emissions of heat-trapping gases. These emissions come mainly from the burning of fossil fuels (coal, oil, and gas), with important contributions from the clearing of forests, agricultural practices, and other activities.”

Therefore, the overwhelming scientific consensus is that climate change is real, that it is being caused by human actions, and that there will be potentially significant impacts for people around the globe.

Climate scientists continue their research to increase knowledge on many aspects of climate change, including predictions about how quickly temperatures are likely to rise, what impact melting glaciers will have on sea level, and whether hurricanes will increase in quantity or intensity. Such information is essential if we are to wisely and effectively mitigate the potential impacts of climate change.

The climate system is extraordinarily complex. Understanding it is a grand scientific challenge — it is also an immensely important one.