Monday, June 18 , 2018, 4:51 am | Fair 51º


Ken Macdonald: The Global Warming Pause That Wasn’t, and New ‘Solutions’

Based on a recent post in Science Express, NOAA scientists have found that the much-ballyhooed pause or hiatus in global warming over the past 15 years did not happen. It was an artifact of the data. The unfortunate bottom line: Global warming has indeed kept steaming along at about the same rate it did in the second half of the 20th century.

Lots of people are unhappy about this. The climate change skeptics are crying foul, and even some of the scientists whose work documents climate change are irked.

Some of them came up with explanations for the pause, and feel now that they look silly. They shouldn’t worry about this, though, because their explanations may still be correct.

For example, the hypothesis that heat has been stored in intermediate-depth ocean waters may be true, and perhaps this heat will emerge in the future as another mysterious “blob” of weirdly warm water, a bit like the one I wrote about in a previous column.

Other scientists are not at all pleased that the needed corrections to the temperature data were not made a long time ago (like 15 years ago would have been good) to avoid all the ensuing confusion and naysaying.

Here’s an example of one of the corrections I know about personally. As a graduate student in oceanography at MIT and Woods Hole Oceanographic Institution in the early 1970s, I was on ships for months at a time steaming across the south Pacific, south Atlantic and Indian oceans. At noon each day, one of my jobs was to throw a bucket over the side, let it fill up with seawater and haul it back on board where I would measure the temperature with a thermometer to the nearest 0.1ºF and record it.

These measurements and many more from other ships around the world were compiled by NOAA.

Subsequently, NOAA relied more on measurements made from buoys deployed around the world, only relying on ship measurements where buoy data were lacking. So eventually (about the year 2000), most of the measurements were acquired from buoys, few from buckets tossed from ships.

The thermometers on buoys stick down into the water and measure the temperature very accurately throughout the day and night. The bucket measurements I participated in were made during the day, and as I hauled the bucket up onto the hot deck and made my measurement, the water was warming up just a little bit.

So, when one compares an earlier era of mostly bucket measurements to a later time of mostly buoy measurements, it will look as if a warming trend has flattened out. But if you correct the bucket measurements, then you get the straight line of increasing surface water temperature seen in the nearby graph.

Since the oceans cover 70 percent of our planet, any correction will have a large effect.

Count me among those who are not pleased that they didn’t think of this a lot sooner. As irritating as this is, though, it is a good example of how scientists do double and triple check what they do very carefully, and when they make mistakes they are honest about corrections even if it makes them look dumb in retrospect.

You can be sure that some people will claim this mistake as a clear reason why scientists cannot be trusted, and those same people will say that all of the scientific climate “data” and “so-called facts” are bunk.

Nevertheless, the inescapable main point is that global warming is real, it has not taken a hiatus for the past 15 years, and the bottom line is that we need to do something about it, and quickly.

Even before this finding, an important committee of the National Academy of Sciences was charged with evaluating various proposed “geo-engineering” solutions for global warming, in case society failed to curb the emissions of greenhouse gases. (Click here to download the full report, available for free at The National Academies Press.)

One idea is to dump iron filings into the ocean, which would stimulate absorption of carbon dioxide by fertilizing blooms of plankton. It turns out that a limiting nutrient in the ocean is iron, and adding just a small amount can cause a large bloom of plankton. This has been tried on a small scale in a few locations, and it works, but it will only help a little. Unintended consequences are a big concern and are being studied carefully, since there is a long history of human “solutions” backfiring badly.

Another more powerful solution is injecting massive amounts of sulfur dioxide into the stratosphere to reduce the amount of incoming solar radiation. This is called “albedo modification.”

Nature provides us with this experiment every time there is a major volcanic eruption. Tons of sulfur dioxide shoot up into the stratosphere and ride wind currents around the world.

In 1991, Mount Pinotubo in the Philippines erupted enough sulfur dioxide (20 million tons) to dim solar radiation by 2 percent to 3 percent for about two years, until the SO2 particles fell out and solar radiation popped back up to normal. (You can see the dip in global warming of about 0.3ºF during 1992-1994 in the nearby graph at the arrowhead).

So if humans try to mimic volcanoes, we would have to inject enormous amounts of this pollutant into the stratosphere on an ever-increasing scale to keep up with CO2 emissions (and never stop).

One big concern is that even if the United States and Europe decide that this is an unacceptable solution, what if some other country (China? Russia?) decides that this is the only way out? Would such massive and deliberate pollution of the global atmosphere be considered an act of war?

This is giving me a headache; I’m going to jump into the unusually warm ocean and go for a swim! I’ll try to think of something more uplifting to write about next time ...

In the meantime, the giant blue whales and humpback whales are having a big party in our very own Santa Barbara Channel this summer. Go out and see them!

— Ken Macdonald is an oceanographer and professor emeritus in UC Santa Barbara’s Department of Earth Science. He has been affiliated with Woods Hole Oceanographic Institution and Scripps Institution of Oceanography, and has led deep-sea dives up to 15,000 feet in the submersible Alvin. He is a naturalist for Channel Islands National Park and the Channel Islands National Marine SanctuaryClick here to read previous columns. The opinions expressed are his own.

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