Energy > Climate Change
Scientific agreement on climate change
This article is part of our series focused on the causes and consequences of a warming planet
People in the US are divided over whether human activity is causing global warming. Some believe it is part of a natural climate cycle that will reverse course in the near future. Others believe that human activity is causing a permanent change in the world’s climate. This article looks at evidence of what climate scientists say, the results of scientific research, position statements of scientific organizations, the results of computer models and more.
Surveys of climate scientists
Several surveys of climate scientists have been conducted over recent decades. These surveys have shown a strong consensus by climate scientists that the planet is warming and the warming is caused primarily by human activity. Examples of organizations conducting these surveys include George Mason University and the American Meteorological Society. The latter survey focused on members of the American Meteorological Society, the American Geophysical Union and the American Association for the Advancement of Science, along with other scientists working in the field.
Survey of climate research
Moving from scientists to the actual scientific research, a 2004 survey of all peer-reviewed research studies on global warming published between 1993 and 2003 (928 studies) showed that when looking just at the studies taking a position on the topic (75% of the studies), the studies all confirmed that human activity causes global warming. The remaining 25% of the studies made no comment either way as they focused on other issues like assessing research methods or historic analysis.
A more recent survey conducted in 2013 of all peer-reviewed global warming research published between 1991 and 2011 (12,000 studies) found that, when looking just at the studies taking a position on the topic (4,000 studies), over 97% agreed that human activity is causing global warming.
Survey of climate organizations
Next consider the position of scientific organizations, most scientific organizations have "position statements" on the topic. An example is the American Meteorological Society; "It is clear from extensive scientific evidence that the dominant cause of the rapid change in climate of the past half century is human-induced increases in the amount of atmospheric greenhouse gases, including carbon dioxide, methane, nitrous oxide and chlorofluorocarbons."
Almost 200 scientific organizations around the world have position statements stating that global warming is primarily attributed to human activity. No national scientific organization position statements were found stating that global warming is not caused by human activity.
Climate computer models
Scientists create computerized models to predict the future of the Earth’s temperature and climate. A climate computer model is a mathematical representation of the physical processes that heat and cool our planet, move heat around, melt ice, create clouds, etc. Numerous climate models have been created by scientists in recent years.
These models are also used to identify the causes of the rapid rise in global temperature that has occurred in recent decades. When all of the naturally occurring factors are included in the models, they fall far short of predicting the current rise in temperature. Only when man-made factors are included in the models do they predict the rapid rise in Earth’s temperature.
This result should not come as a surprise. Increases and decreases of greenhouse gas concentrations have caused changes in global temperature many times over millions of years, including mass extinctions and ice ages. This linkage is so strong that any attempt to attribute the current warming to other causes must also explain why the current warming is not caused by the greenhouse effect.
The near-Earth atmosphere (troposphere) is warming while the upper atmosphere (stratosphere) is cooling. So, scientists know that the Earth’s warming must be something that traps heat next to the surface of the planet and does not let the heat move higher in the atmosphere. This phenomenon eliminates many of the potential natural causes of warming. Only the greenhouse effect traps heat in the lower atmosphere. And the greenhouse effect is being driven by carbon dioxide and other gases that we are releasing into the atmosphere.
See the Ag Decision Maker website for more from this series.
Don Hofstrand, retired extension agricultural business specialist, firstname.lastname@example.org
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University