Science FAQs
Isn’t there a scientific consensus that global warming is real and bad for us?
- There is no "scientific consensus" that global warming will cause damaging climate change. Claims that there is such a consensus mischaracterize the scientific research of bodies like the United Nations Intergovernmental Panel on Climate Change (IPCC) and the U.S. National Academy of Sciences (NAS).
What do scientists agree on?
- Scientists do agree that: 1) global average temperature is about 0.6°Celsius—or just over 1° Fahrenheit—higher than it was a century ago; 2) atmospheric levels of carbon dioxide (CO2 ) have risen by about 30 percent over the past 200 years; and 3) carbon dioxide, like water vapor, is a greenhouse gas whose increase is likely to warm the Earth’s atmosphere.
Doesn’t this mean we should be worried?
- As Richard Lindzen of MIT summarized it in The Wall Street Journal, "These claims are true. However, what the public fails to grasp is that the claims neither constitute support for alarm nor establish man’s responsibility for the small amount of warming that has occurred. In fact, those who make the most outlandish claims of alarm are actually demonstrating skepticism of the very science they say supports them. It isn’t just that the alarmists are trumpeting model results that we know must be wrong. It is that they are trumpeting catastrophes that couldn’t happen even if the models were right as justifying costly policies to try to prevent global warming." [Emphasis in original]
What don’t scientists know yet?
- Scientists do not agree on whether: 1) we know enough to ascribe past temperature changes to carbon dioxide levels; 2) we have enough data to confidently predict future temperature levels; and 3) at what level temperature change might be more damaging than beneficial to life on Earth.
Didn’t the National Academy of Sciences say greenhouse gases cause global warming?
- The National Academy of Sciences reported in 2001 that, "Because of the large and still uncertain level of natural variability inherent in the climate record and the uncertainties in the time histories of the various forcing agents…a causal linkage between the buildup of greenhouse gases in the atmosphere and the observed climate changes during the 20th century cannot be unequivocally established." It also noted that 20 years’ worth of data is not long enough to estimate long-term trends.
Hasn’t the Earth warmed precipitously over the past 100 years?
- The temperature rise of 0.6°C over the last century is at the bottom end of what climate models suggest should have happened. This suggests that either the climate is less sensitive to greenhouse gases than previously thought or that some unknown factor is depressing the temperature.
Don’t climate models warn of alarming future warming?
- Predictions of 6°C temperature rises over the next 100 years are at the extreme end of the IPCC range, and are the result of faulty economic modeling, not science (see economics section below).
What are the realistic current estimates of future warming?
- Both James Hansen of NASA—the father of greenhouse theory—and Richard Lindzen of MIT—the most renowned climatologist in the world—agree that, even if nothing is done to restrict greenhouse gases, the world will only see a global temperature increase of about 1°C in the next 50-100 years. Hansen and his colleagues "predict additional warming in the next 50 years of 0.5 ± 0.2°C, a warming rate of 0.1 ± 0.04°C per decade."
What about satellite temperature measurements?
- Evidence from satellite and weather balloon soundings suggests that the atmosphere has warmed considerably less than greenhouse theory suggests. These measurements, which cover the whole atmosphere and show only a very slight warming, show a disparity with the surface temperature measurements, which cover only a small fraction of the Earth but show sustained warming.
Hasn’t the disagreement between satellite and surface temperatures been resolved?
- No. There is still substantial disagreement between the mid-range of the satellite measurements and the mid-range of the surface measurements. This presents a problem for climate models.
Do other man-made factors besides greenhouse gases influence temperature?
- New research suggests that the role of greenhouse gases in warming has been overestimated, as factors like atmospheric soot, land use change, and solar variation9 all appear to have contributed significantly to recent warming.