Ask Don Paul: Could we already be close to some climate tipping ... - Buffalo News

Ask Don Paul: How close are we to climate tipping points?

I have generally accepted the scholarly guidance from leading climate scientists, atmospheric chemists and physicists that the window on steering us away from the worst case scenarios of global warming impacts is narrowing, but has not yet closed.

The goal of not surpassing a global mean temperature increase of 1.5 degrees Celsius since pre-industrial temperatures is becoming more unlikely to fulfill. Fossil fuel use and our agricultural technologies along with greenhouse gas feedback mechanisms triggered by human activity-caused warming are making the closing of that window more likely, though not yet certain. For a brief refresher on the irrefutable evidence of human-linked warming, here is a short read from the climate scientists at NASA.

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"Before I go any further discussing Earth’s eventual deadly climate fate (in the distant future but sooner than you may have heard), we have to look first at the basics of what turned Venus into a lifeless furnace," Paul writes.

Here are the most likely impacts from the warming.

On the other hand, some leading climate scientists, such as Michael Mann, still hold out some hope for mitigation of the worst effects, with the proviso that we begin moving more aggressively away from fossil fuels and from some of the ways we grow food and raise livestock. Mann, who has often been criticized by non-scientist warming climate deniers, wrote this on Facebook concerning “doomism”: “I have to say that I am not a fan of this sort of doomist framing. It is important to be up front about the risks of unmitigated climate change, and I frequently criticize those who understate the risks. But there is also a danger in overstating the science in a way that presents the problem as unsolvable, and feeds a sense of doom, inevitability and hopelessness.”

Some new and potentially more pessimistic possibilities crossed my eyes in a personal essay by Cambridge professor emeritus Michael Edgeworth McIntyre, in the publication Physics Today. McIntyre's expertise is in fluid dynamics, a physical science that is very much a part of meteorology and climate science modeling. He begins with a premise that can hardly be denied: “Arguably, the climate problem is by far the most complex of all the problems confronting humanity today.” While writers like me try to streamline those complexities for the reader, McIntyre points out that the reality is the climate problem involves human behavior, global-scale atmospheric and oceanic circulations down to the scale of cyclones, thunderstorms, forest canopies, soil, phytoplankton, bacteria and even further down to molecular isotopes. This is only a partial list of the many variables involved.

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The U.S. has the most tornadoes by far of any nation.

McIntyre and fluid dynamics demonstrate that even ice sheets “flow and melt or shatter in dauntingly complex ways, which elude accurate modeling.” Many climate scientists try to put aside some of the smaller scale complexities, viewing them as less important in the big picture. Climate models, which continue to improve, are designed to blot out the “noise” of individual storms and short-lived weather patterns to determine the broader nature of the big picture. By necessity, they are not high-resolution models, such as the meteorological models we use to detail placement and intensity of lake effect snow bands or thunderstorms.

The climate models since the 1980s have done a good job of painting the big picture, although they have often underestimated the rate of warming, rising sea levels and climate-related weather extremes. Overall, the pace of global warming on land and in the oceans has been relatively well-predicted in these models, if understated.

But McIntyre points out there is an abundance of paleoclimate data developed from sediment and ice cores going back hundreds of thousands of years of more rapid-fire past changes, which would be much less likely to show up in current climate modeling.

"While water supply problems in the far west have improved tremendously, the interior of the West and the critical Colorado River Basin remain in crisis," writes Don Paul.

Such evidence conclusively shows there have been past warmings in the North Atlantic of as much as 10 degrees Celsius. In some cases, McIntyre says such warmings took only a “few years” to occur, which are nearly “instantaneous from a climate-system perspective.”

Some of these rapid changes are related, in particular, to reductions in Nordic sea ice between Scandinavia and Greenland. The paleoclimate data show in detail that these warmings have progressed with incredible speed before human activity was a factor, and was also tied to natural greenhouse gas increases in carbon dioxide and methane. Today, it is humanity’s drastic increase in greenhouse gas output since the industrial revolution at play, not natural forcing. The rate of carbon dioxide increases since 1750 is unparalleled in the last 850,000 years.

McIntyre and some of his colleagues have concerns that climate models lack the detailed resolution to pick up on these rapid warmings in time scale or detail. There may be tipping points that the models will miss in the near future, even as weather extremes continue to amplify and multiply. These tipping points are apart from the broad and dangerous path for the Earth’s climate already underway.