Global Science Report is a 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.”
Global warming beater Justin Gillis of the New York Times had an article yesterday describing a new paper in the current issue of Nature magazine, the point of which seems to be scaring people with alarming global warming statistics.
Gillis’ article “By 2047, Coldest Years May Be Warmer Than Hottest in Past,” describes the results of a class-project-cum-Nature-article headed by Camilo Mora from the University of Hawaii at Manoa (please, no puns). The class assignment was to identify the year for each spot on the globe in which all future years were, according to climate model projections, warmer as a result of greenhouse gas emissions than the warmest year simulated by the models during the historical period 1860 to 2005. Mora and students termed this pivotal year the “climate departure.”
This work is significant, according to Gillis, because:
Thousands of scientific papers have been published about the model results, but the students identified one area of analysis that was missing. The results are usually reported as average temperature changes across the planet. But that gives little sense of how the temperature changes in specific places might compare with historical norms. “We wanted to give people a really relatable way to understand climate,” said Abby G. Frazier, a doctoral candidate in geography.
Perhaps Dr. Mora should have injected a little climate-science history in this class.
Looking at the time that a human climate signal will rise above the background noise is not particularly a novel concept. It’s commonplace. We would guess that a signal-to-noise ratio was probably present in the first papers describing the performance and output of the very first climate models.
After all, without such information it is impossible to put absolute changes in perspective. Some measure of the statistical significance of climate change has been present in every climate assessment report from the U.N. Intergovernmental Panel on Climate Change dating back to 1990.
In our presentation to the Science Policy Conference of the American Geophysical Union this summer, we even included a table listing the number of years into the future it would be before projected changes in precipitation across the U.S. rose above the level of nature variability. We guess we just didn’t give that year a catchy enough name like “climate departure,” because our results didn’t capture the attention of the press (nor were they very frightening).
But Gillis does manage to carve some new, scary Jack-o-Lanterns from the Mora study.
Here is his lead paragraph:
If greenhouse emissions continue their steady escalation, temperatures across most of the earth will rise to levels with no recorded precedent by the middle of this century, researchers said Wednesday.
Uh, correct us if we are wrong, but we already thought that global temperatures were reported to be at unprecedented levels in recorded history. According to the IPCC’s Fifth Assessment Report:
Each of the last three decades has been successively warmer at the Earth’s surface than any preceding decade since 1850.
So, is this recycled news, or is the new paper saying that we have to wait until 2047 for that to happen? Well, whatever, it sounds B-A-D.
Or how about this one:
“Go back in your life to think about the hottest, most traumatic event you have experienced,” Dr. Mora said in an interview. “What we’re saying is that very soon, that event is going to become the norm.”
Hot Tub Time Machine came immediately to mind, but Gillis provided another scenario:
With the technique the Mora group used, it is possible to specify climate departure dates for individual cities. Under high emissions, climate departure for New York City will come in 2047, the paper found, plus or minus the five-year margin of error.
How scared should you be about passing the date of “climate departure”?
Not at all.
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