Some days there’s good news or bad, and then there are the days that deliver gut punches. A case of the latter comes from Expect 1,000-year climate impacts, experts say:
Even if the world can cap carbon dioxide emissions tied to global warming, expect to see droughts and sea level rise that span centuries, not just decades, according to a new study sponsored by the U.S. government.
“People have imagined that if we stopped emitting carbon dioxide the climate would go back to normal in 100 years, 200 years; that’s not true,” lead author Susan Solomon told reporters.
Instead, the team concluded, warming tied to higher CO2 “is largely irreversible for 1,000 years after emissions stop.”
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Climate change has been driven by gases in the atmosphere that trap heat from solar radiation and raise the planet’s temperature – the “greenhouse effect.” Carbon dioxide has been the most important of those gases because it remains in the air for hundreds of years. While other gases are responsible for nearly half of the warming, they degrade more rapidly, Solomon said.
Before the industrial revolution the air contained about 280 parts per million of carbon dioxide. That has risen to 385 ppm today, and politicians and scientists have debated at what level it could be stabilized.
The peer-reviewed study concludes that if CO2 is allowed to peak at 450-600 parts per million, the results would include persistent decreases in dry-season rainfall that are comparable to the 1930s U.S. Dust Bowl in zones including the U.S. southwest, southern Europe, Africa, eastern South America and western Australia.
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Warmer climate also is causing expansion of the ocean and that factor alone is likely to lock in a 1.3 to 3.2 foot sea level rise by the year 3000 if CO2 peaks at 600 ppm, and double that if it peaks at 1,000 ppm, the researchers calculated.
“Additional contributions to sea level rise from the melting of glaciers and polar ice sheets are too uncertain to quantify in the same way,” Solomon said in a statement. “They could be even larger but we just don’t have the same level of knowledge about those terms. We presented the minimum sea level rise that we can expect from well-understood physics, and we were surprised that it was so large.”
Solomon noted that while global warming has been slowed by the oceans, which absorb carbon, that positive effect will wane over time and eventually oceans will actually warm the planet by giving off their accumulated heat to the air.
Alan Robock, of the Center for Environmental Prediction at Rutgers University, agreed with the report’s assessment.
“It’s not like air pollution where if we turn off a smokestack, in a few days the air is clear,” said Robock, who was not part of Solomon’s research team. “It means we have to try even harder to reduce emissions,” he said.
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While scientists have been aware of the long-term aspects of climate change, the new report highlights and provides more specifics on them, said Kevin Trenberth, head of climate analysis at the National Center for Atmospheric Research.
“This aspect is one that is poorly appreciated by policymakers and the general public and it is real,” said Trenberth, who was not part of the research group.
“The temperature changes and the sea level changes are, if anything underestimated and quite conservative, especially for sea level,” he said.
While he agreed that the rainfall changes mentioned in the paper are under way, Trenberth disagreed with some details of that part of the report.
“Even so, there would be changes in snow (to rain), snow pack and water resources, and irreversible consequences even if not quite the way the authors describe,” he said. “The policy relevance is clear: We need to act sooner … because by the time the public and policymakers really realize the changes are here it is far too late to do anything about it. In fact, as the authors point out, it is already too late for some effects.”
I’ve long contended that two of the most problematic conceptual hurdles people have in dealing with energy and environmental issues are non-linearities and long time lags. This article highlights both of these issues. The non-linearities arrive in the form of positive feedbacks–we pump a little CO2 into the atmosphere and get almost no climate change. Emit a little more, you get some warming, but nothing to lose sleep over. Just a little more, and you start to see drought and other effects, as well as melting glaciers and polar ice (which decrease the reflectivity of large patches of the Earth’s surface), changes in the oceans’ ability to absorb CO2, and the next thing we know we’re flirting with the possibility of massive methane releases and some truly hideous consequences.
The time lags are just as nasty, in that they require us to take serious action long before “things get really bad”. And that requires us to get the science right and then find the collective courage to trust the experts like Susan Solomon and James Hansen who deliver the alarming, if not alarmist, news. As we seem to be just learning, there is also a nasty time lag between when we take action and when we see results, which raises the whole topic of adaptation to rising sea levels and temperatures, and significant reductions in the availability of fresh water where and when we’ve always counted on it.
I also feel compelled to touch on a couple of other points, which (sadly) tie into this article.
Notice the statement quoted above about science focusing on a rise in atmospheric CO2 to 450 to 600 parts per million. I still contend that the people ringing the alarm about 350 ppm being the “safe” upper limit aren’t getting enough attention. I strongly suspect that this is one of those truly inconvenient truths that will only gain wide acceptance over time–time we really don’t have to spare.
Also, the article mentions (in an unquoted section) that the study doesn’t consider geoengineering to pull CO2 out of the atmosphere. This study and my view of 350 being the “magic” number only strengthen my belief that we will resort to several geoengineering “fixes” (i.e. global hacks/displays of monumental hubris and desperation), possibly some to pull CO2 out of the air and some to block some sunlight from reaching the Earth’s surface (or reflecting it back into space).
It seems humanity has yet to learn the first two laws of holes:
1. When you’re already in a hole, stop digging!
2. The deeper the hole you’re in, the harder (or more painful or more expensive or …) it is to climb back out.
