The Earth is warming, and human activity is probably contributing to it. Even if this warming turns out to be short-term on a geophysical scale, it will have huge effects on health, and culture and economies worldwide. Unfortunately, many intelligent people, some with political agendas and some merely wrong-headed, argue that there is no broad scientific consensus about global warming and its causes.
I submit the following as evidence for that broad scientific consensus.
First, from the US Dept. of Energy, some background on greenhouse gases:
“In the U.S., our greenhouse gas emissions come mostly from energy use. These are driven largely by economic growth, fuel used for electricity generation, and weather patterns affecting heating and cooling needs. Energy-related carbon dioxide emissions, resulting from petroleum and natural gas, represent 82 percent of total U.S. human-made greenhouse gas emissions.” Link
Next, evidence of climate change from the Intergovernmental Panel on Climate Change (IPCC):
“An increasing body of observations gives a collective picture of a warming world and other changes in the climate system.” Link
From a National Research Council report commissioned by the Bush Admistration which looked into, among other things, the IPCC’s conclusions:
“With regard to the basic question of whether climate change is occurring, the [IPCC] report notes that measurements show that temperatures at the Earth’s surface rose by about 1 degree Fahrenheit (about .6 degrees Celsius) during the 20th century. This warming process has intensified in the past 20 years, accompanied by retreating glaciers, thinning arctic ice, rising sea levels, lengthening of the growing season in many areas, and earlier arrival of migratory birds. [The IPCC's conclusion that] the global warming that has occurred in the last 50 years is likely the result of increases in greenhouse gases accurately reflects the current thinking of the scientific community [although] uncertainties about this conclusion remain.” [Emphasis added] Link
“Greenhouse gases are accumulating in Earth’s atmosphere as a result of human activities, causing surface air temperatures and sub-surface ocean temperatures to rise. Temperatures are, in fact, rising. The changes observed over the last several decades are likely mostly due to human activities, but we cannot rule out that some significant part of these changes is also a reflection of natural variability.” Link
Next, the American Geophysical Union:
“The global climate is changing and human activities are contributing to that change. Scientific research is required to improve our ability to predict climate change and its impacts on countries and regions around the globe.” Link
And the American Meteorological Society:
“There is convincing evidence that since the industrial revolution, human activities, resulting in increasing concentrations of greenhouse gases and other trace constituents in the atmosphere, have become a major agent of climate change.” Link
Finally, from the American Association for the Advancement of Science:
“Governments and consumers in the United States and worldwide should take immediate steps to reduce the threat of global warming and to prepare for a future in which coastal flooding, reduced crop yields and elevated rates of climate-related illness are all but certain.” Link
“Strong new evidence shows that ocean temperatures are rising because of human activity.” Link