June 27, 2013 12:12PM

Climate vs. Climate Change

Global Science Report is a weekly feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our monthly “Current Wisdom.”

There seems to be a fundamental misunderstanding in the difference between climate and climate change.

This is on very public display in the president’s recently unveiled Climate Action Plan, which details a series of executive actions designed to reduce greenhouse gas emissions in an attempt to control the future course of the climate.

In justifying the need for these actions, and why he doesn’t have time to wait for Congress to act, the president points to numerous recent examples of extreme weather disasters while linking weather extremes to climate change brought about by anthropogenic greenhouse gases emissions.

In doing so, he goes awry of the best science.

Here’s why.

The natural climate of the U.S. includes all manner of extreme weather events—hurricanes, tornadoes, droughts, floods, heatwaves, cold outbreaks, derechos, and virtually every other type of bad weather you can dream up.

This is true now, just as it was 100 years ago, before greenhouse gases were being emitted to the atmosphere in large quantities from human activities—primarily the burning of fossil fuels to produce energy.

Human-caused climate change is an incremental pressure to slightly alter the character of weather events, for example, their frequency and/or magnitude. This includes weather events both extreme and otherwise. The nature of this alteration, if it occurs at all, is scientifically uncertain for most types of weather.

In other words, every time there is some sort of weather “disaster” you don’t need to invoke climate change to explain it. A simple climate explanation will usually suffice. In fact, bringing climate change into the explanation usually runs afoul of our current scientific understanding. It is as easy to argue that climate change mitigates (or even averts) weather disasters as it is to argue that it augments them.

But folks pushing for greenhouse gas regulations don’t often let the facts get in the way.

This includes the president, as well as many of his federal advisors.

For example, Roger Pielke Jr., a leader in the field of weather disaster trends, tweeted this about the president’s speech on Tuesday:

@RogerPielkeJr “Will be interesting to see if anyone on the side of climate action will care that Obama's plan begins w/ false claims about disaster trends”

And in our recent review of the draft version of the government’s latest National Assessment report, we point out the pervasive confusion between climate and climate change within the report. For example, regarding impacts on the transportation sector, we note:

It is not climate change, but the vagaries of the climate itself that have the greatest impact on U.S. transportation. Climate change, to the degree that it is detectable and identifiable, contributes a mix of impacts, some positive and some negative, and the net impact has never been reliably quantified or monetized.

The impacts of climate and climate change are confused and thus used interchangeably, however, such usage is incorrect and misleading.

Perhaps the biggest reason why it is easy to confuse climate and climate change, is that it appears that the weather is getting worse—that is, there are more, and more costly, extreme weather events. The climate must be changing to make this happen, right?


What is changing, besides increased media (both mainstream and social) coverage, is that there are more people, with more (valuable) stuff, in harm’s way.

So, even in a constant climate, the frequency and magnitude of extreme weather events—such as those included in the government’s annual list of “Billion Dollar Weather/Climate Disasters”—will increase.

Yet the president points to this increase and links it to human-caused climate change.

This is wrong, and this is what Roger Pielke Jr. was referring to in his tweet.

And Roger should know. He has jus published a paper examining trends in tornado losses in the U.S. from 1950 through 2011. It shows that while raw damage has been on the rise, when adjusted for socioeconomic changes (like population, income, housing units, GDP), there has actually been a sharp decline. Further, the decline in damages may in fact be related with a decline in strong tornado events, although the data are not robust enough to know for sure. Quoting from the conclusions of is paper:

The analysis presented in this paper indicates that normalized tornado damage in the US from1950 to 2011 declined in all three normalization methods applied (two are statistically significant one is not). The degree to which this decrease is the result of an actual decrease in the incidence of strong tornadoes is difficult to assess due to inconsistencies in reporting practices over time. However, an examination of trends within sub-periods of the dataset is suggestive that some part of the long-term decrease in losses may have a component related to actual changes in tornado behaviour. Further research is clearly needed to assess this suggestion.

Roger has also studied losses from hurricanes and floods and in both cases found that once demographics changes are taken into account the upward trend in losses disappears.

So the science shows that increasing losses from extreme weather events is caused by more people and more wealth, but the president tells us that it is a result of human-caused climate change and invokes executive action to try to stop it.

His efforts are doomed to fail from the outset (assuming his Climate Action Plan doesn't drive down the population or the economy). 


Downton, M.W., Miller, J. Z. B., and R. A.  Pielke, Jr., 2005. Reanalysis of the U.S. national flood loss database. Natural Hazards Review, 6, 13–22.

Pielke, Jr., R. A., Gratz, J., Landsea, C. W., Collins, D., Saunders, M., and R. Musulin, 2008. Normalized hurricane damages in the United States: 1900–2005. Natural Hazards Review, 9(1), 29–42.

Simmons, K. M., Sutter, D., and R. Pielke, Jr., 2012. Normalized tornado damage in the United States: 1950–2011. Environmental Hazards, doi: 10.1080/17477891.2012.738642.