This post is by Jed Lewison from Daily Kos
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A new study indicates that climate scientists may have underestimated the amount of global warming that has already occurred by as much as 20 percent. But that doesn’t mean that it’s any hotter outside. It’s a matter of hotter relative to what?
Preventing global warming from becoming “dangerous” may have just got significantly harder after new research suggested climate scientists have been using the wrong baseline temperature.
Scientists haven’t been making some kind of mistake in measuring the temperature. The issue is time. Most climate change models start somewhere in the 19th century, with the best data set beginning around 1880. But this new study indicates that this date may actually be too late if the intent is to really capture all the impact burning of fossil fuels has had on the climate. By the late 1800s, people had already been burning fossil fuels in rapidly-increasing amounts to stoke the
of the industrial revolution. That early consumption of coal and oil may have had more impact than previously thought.
Naturally, taking fuller account of this preindustrial warming also makes it much more likely that we’ll pass 1.5 degrees Celsius of warming. That’s an extremely challenging target for us to hit in limiting warming that many observers and analysts have already written off, although it is cited as a more lofty goal in the Paris climate agreement.
Meeting a 1.5° C target is obviously more difficult if the change already experienced is 1.2 degrees rather than the 1.0 that had been broadly accepted. The new information doesn’t make the world any warmer, but it could have an effect on programs designed to meet the 1.5 degree goal. Either the total change allowed under agreements needs to go up to adjust for this early change, the definition of the allowed change needs to be redefined to make it clear it’s relative to 1880, or programs will have to be rapidly accelerated to try and hold off that final bit of change.