Imprecision of the Phrase “Global Warming”

Guest Contribution by Michael Tobis, University of Chicago

Consider the possibility that the expression “global warming” has become a problematic one, and that it might be best to avoid it.

A big part of the public confusion about climate change comes from sloppy language. The naysayers prey on this confusion, very much as their peers prey on the phrase “evolutionary theory” to suggest that “evolution, well, it’s just a theory”.

Scientists use “global warming” precisely, to mean “a tendency for the globe to warm over a given period”. Thus, in the question of human impacts, we discuss what proportion of the observed “global warming” in recent years is anthropogenic, what the magnitude of the “global warming” due to anticipated radiative forcing scenarios will be in the future, and the nature of climate change expected for a given “global warming”. In each case, we usually mean by this phrase precisely and only an increase in the mean global temperature.

I imagine I’m not alone in finding myself in a quandary when someone asks if I “believe in” global warming. Imagine asking an economist whether they “believe in” inflation. Where does one begin?

This problem arises from confusion (to some extent deliberately engendered) in the public as to what the term means.

If someone asks me in my capacity as a climate scientist whether I “believe in “global warming”, they are not asking the question in a literal sense. They are asking “what am I to make of this confusing topic called “global warming”?

In the end they are usually asking some combination of questions like 1) whether greenhouse gases are accumulating? 2) whether the greenhouse effect is established science? 3) whether global warming has been observed? 4) whether future climate change is expected to be big enough to worry about? 5) whether cooling at a single location falsifies the “theory”? 6) whether to expect super-hurricanes? 7) whether the Gulf Stream will shut down instantly glaciating Scandinavia and Britain? 8 ) how you can model climate when you can’t predict weather? etc. Often they will bounce incoherently from one to another of these sorts of exasperatingly-missing-the-point sorts of question.

Once in a while someone will have more sophisticated questions like 1) what’s the magnitude of the anthropogenic forcing compared to natural forcings? 2) what’s the lag time in the system response? 3) what is the magnitude of the most disruptive plausible scenarios? 4) what’s the likelihood of the discontinuous shifts in system regime? etc., When I hear people asking the right questions it makes my day, but it’s pretty rare.

What people outside the field universally don’t mean by “global warming” though, is “a tendency for the global mean surface temperature to increase”!

I believe that this site has made some progress by proposing a working definition of the scientific consensus.

Usually, when asked whether one “believes in” global warming, the best answer is to state that there is a scientific consensus and a formal process for developing it, and what that consensus is. For a sophisticated audience, one can go on to explain why consensus should drive policy and should not drive science, and what steps can be taken to ensure that this happens.

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