No planet for optimists: Coastal flooding may come sooner than we fear

When it comes to global warming, what else don’t we know? What science does know, and what it can infer from studying archeological records, already makes anybody who thinks the long-term habitability of Earth is more important than short-term profits very worried.

One detail that may have been under-appreciated is meltwater. Melting ice sheets, especially in Greenland and Antarctica, is well understood to raise the sea level. But the effects might not be simply the additional water added to the oceans. In this scenario, the melted freshwater will additionally increase warming, thereby creating a feedback loop that will accelerate the loss of polar ice sheets, thus accelerating the rate of sea-level rise. How fast? Fast enough that the sea level could rise “several meters” in 50 to 150 years.

This sobering prediction of what might happen without a drastic reduction in greenhouse-gas emissions is the conclusion of 19 climate scientists from the United States, France, Germany and China who studied the effect of growing ice melt from Greenland and Antarctica through the use of climate simulations, paleoclimate data and modern observations. The paper, published in Atmospheric Chemistry and Physics and led by James Hansen, concludes that swift action is necessary in the face of a “global emergency.”

Icebergs breaking off glaciers at Cape York, Greenland (photo by BrockenInaGlory)

Predictions of a future catastrophic rise in the oceans, threatening to drown many of the world’s biggest cities, are by now far from novel. Two other recent papers conclude that humanity has already committed itself to a six-meter rise in sea level because of the greenhouse gases already thrown into the atmosphere and the retention and later slow release of much of those gases by the world’s oceans. A study in the journal Science estimates that more than 444,000 square miles of land, where more than 375 million people live today, would be inundated by such a rise.

Compare that to the complacency of the world’s governments at the Paris Climate Summit in December 2015. Despite a thunder of plaudits from the corporate media, the governments committed themselves to goals that, even if achieved, would lead to a global temperature rise of nearly 3 degrees Celsius by 2100, with further increases beyond that. That is far beyond the goal of 1.5 degrees set at the summit. But even the summit’s actual modest goals are not necessarily attainable because peer pressure is the primary mechanism to induce compliance; there are no binding legal agreements.

Feedback loops accelerate ice-sheet melting

The Atmospheric Chemistry paper says that sea level was at times six to nine meters higher than today approximately 115,000 years ago when the average global temperature “probably was only a few tenths of a degree warmer than today.” Ice-sheet stability may be a key to understanding rapid sea-level rise, the authors write.

The injection of added freshwater into the oceans from faster ice-sheet melting reduces the mixing of ocean waters, causing warmer water to remain at lower depths and thus making warmer water more available to melt the remaining ice shelves. This additional impact of meltwater on the global climate and its feedbacks had not been appreciated before, the authors write. They summarize this as follows:

“Our principal finding concerns the effect of meltwater on stratification of the high-latitude ocean and resulting ocean heat sequestration that leads to melting of ice shelves and catastrophic ice sheet collapse. Stratification contrasts with homogenization. Winter conditions on parts of the North Atlantic Ocean and around the edges of Antarctica normally produce cold, salty water that is dense enough to sink to the deep ocean, thus stirring and tending to homogenize the water column. Injection of fresh meltwater reduces the density of the upper ocean wind-stirred mixed layer, thus reducing the rate at which cold surface water sinks in winter at high latitudes.”

Existing models, including the authors’ own, underplays this mixing effect, the paper states, and thus anthropogenic warming “may be even more imminent than in our model.” Regardless of the exact timing, a tipping point will be reached:

“If the ocean continues to accumulate heat and increase melting of marine-terminating ice shelves of Antarctica and Greenland, a point will be reached at which it is impossible to avoid large-scale ice sheet disintegration with sea level rise of at least several meters. The economic and social cost of losing functionality of all coastal cities is practically incalculable.”

What might happen if the global temperature rises 2 degrees C. from pre-industrial levels? The possibilities are:

“Continued high fossil fuel emissions this century are predicted to yield (1) cooling of the Southern Ocean, especially in the Western Hemisphere; (2) slowing of the Southern Ocean overturning circulation, warming of the ice shelves, and growing ice sheet mass loss; (3) slowdown and eventual shutdown of the Atlantic overturning circulation with cooling of the North Atlantic region; (4) increasingly powerful storms; and (5) non-linearly growing sea level rise, reaching several meters over a timescale of 50–150 years. These predictions, especially the cooling in the Southern Ocean and North Atlantic with markedly reduced warming or even cooling in Europe, differ fundamentally from existing climate change assessments.”

A cold and arid Europe

The authors cite evidence that at the end of the interglacial period in which sea level was believed to be six to nine meters higher than today, there was a dramatic cooling in northern Europe, estimated at 3 degrees C. in summer and 5 to 10 degrees in winter in southern Germany, accompanied by four centuries of arid weather and a decline in trees. During the period of sea-level rise, the North Atlantic is also believed to have suffered from more severe storms, with archeological evidence from Bermuda and the Bahamas used as evidence.

Atmospheric carbon dioxide levels for the past 800,000 years (Graphic by the Scripps Institution of Oceanography at the University of California, San Diego)

As a consensus for global warming emerges, there is less certainty that capping global temperature increase at 2 degrees would be “safe”; thus the Paris Climate Summit’s surprise conclusion to set a goal of a 1.5-degree limit. To achieve such a goal, however, would, as noted above, require cuts to greenhouse-gas emissions far beyond anything pledged. The studies indicating that humanity has already committed itself to a six- to nine-meter sea-level rise imply that temperatures will rise past 1.5 degrees as greenhouse gas-generated heat trapped by the oceans is slowly released into the atmosphere over many decades, if not centuries.

There is no alternative to a massive change to industrial activity — no amount of re-forestation can come close to canceling out the effect of industrial activity.

The Atmospheric Chemistry paper concludes with this sober assessment:

“There is a possibility, a real danger, that we will hand young people and future generations a climate system that is practically out of their control. We conclude that the message our climate science delivers to society, policymakers, and the public alike is this: we have a global emergency. Fossil fuel CO2 emissions should be reduced as rapidly as practical.”

Unfortunately, we live in an economic system that requires constant growth and offers no alternative work for those whose jobs would be eliminated were we to shut down the most polluting industries. In one of his novels, Arthur C. Clarke wrote of a 23rd century world that was finally eliminating the clutter and pollution of the 20th century. Sad to say, the late science fiction master was overly optimistic.

We may have already committed ourselves to 6-meter sea-level rise

Even if humanity were to stop throwing carbon dioxide and methane into the atmosphere today, a catastrophic rise in sea levels of six meters may be inevitable. Two previous prehistoric interglacial periods, in which the carbon dioxide content of the atmosphere was believed to be about what it is today, resulted in dramatic rising of the oceans.

High-latitude ice sheets are melting, and given that global warming is most pronounced in the Arctic, it may already be too late stop a rise in sea levels that would flood out hundreds of millions around the world. Two new papers, the latest in a series of scientific studies, paint a picture considerably less rosy than conventional ideas that major damage can still be avoided.

Heat energy of oceans in 2014 as compared with the 20-year average (graphic by the U.S. National Oceanic and Atmospheric Administration)

One of these papers, a nine-scientist report led by geologist Andrea Dutton at the University of Florida published in the journal Science, found that modest rises in global temperatures in the past led to sea levels rising at least six meters. She summarized the findings this way to Climate Central:

“Even if we meet that 2°C target, in the past with those types of temperatures, we may be committing ourselves to this level of sea level rise in the long term. The decisions we make now about where we want to be in 2100 commit us on a pathway where we can’t go back. Once these ice sheets start to melt, the changes become irreversible.”

Professor Dutton was referencing the widely held belief that catastrophic damage can be avoided if global warming is held to no more than 2 degrees C. from pre-industrial levels. The “permissible” level may be less than that, however. More sophisticated “sea-level reconstructions” through interdisciplinary studies of geological evidence and better understanding of the behavior of ice sheets enabled the paper’s authors to infer that temperatures only slightly higher than what we are experiencing today upset the climatic balance. A summary of the paper concludes:

“[D]uring the last interglacial — a warm period between ice ages 125,000 years ago — the global average temperature was similar to the present and this was linked to a sea-level rise of 6-9 meters, caused by melting ice in Greenland and Antarctica. Around 400,000 years ago, when global average temperatures were estimated to be between 1 to 2°C higher than preindustrial levels, sea levels reached 6-13 meters [higher.]”

“Small” changes have big consequences

More alarming, the level of carbon dioxide in the atmosphere then was lower than it is today. Although geological forces pushing and pulling Earth’s surface can’t be precisely calculated, and thus introduce uncertainty in the actual level of the oceans in the geologic record, the greater uncertainty lies at the higher level of estimates. The paper’s summary said:

“Noticeably, during these two periods, carbon dioxide in the atmosphere remained around 280 parts per million (ppm). The scientists  also looked at sea level during the Pliocene, three million years ago, when carbon dioxide levels reached around 400 ppm — similar to today’s levels. They hypothesized that sea level was at least 6 metres higher than today and potentially substantially higher. … While the global average temperature rises of 1 to 3°C seem small, they were, like today, linked with magnified temperature increases in the polar regions which sustained over many thousands of years.”

A second paper, State of the Climate in 2014, reports that Arctic sea-surface temperatures are rising faster than overall global temperatures, ice caps across the Northern Hemisphere continue to shrink, record high permafrost temperatures are being recorded in northern Alaska and melting of the Greenland ice cap is accelerating. The paper, a collaboration of 413 scientists from 58 countries, reports that, even if greenhouse gases were frozen at current levels, the oceans would continue to warm for centuries and thus lead to rising sea levels.

Carbon dioxide thrown into the air stays in the atmosphere for a long time and warming oceans will retain added heat and transfer that back to the atmosphere. This is already leading to warming oceans, State of the Climate reports:

“Increasing concentrations of greenhouse gases are preventing heat radiated from Earth’s surface from escaping into space as freely as it used to; most of the excess heat is being stored in the upper ocean. As a result, upper ocean heat content has increased significantly over the past two decades.”

The Science and State of the Climate papers back previous studies that conclude “there is no going back” — the excess heat stored in oceans will be released back into the atmosphere for centuries to come — and that Earth is crossing multiple points of no return.

Ice melts in front of our eyes

Two worrisome trends are that the eight lowest Arctic Ocean sea-ice extents have all occurred in the past eight years, and that the extent of the melting of the Greenland ice sheet during summer 2014 was faster than the 1981-to-2000 average 90 percent of the time. Antarctic ice is not yet showing accelerated melting, State of the Climate reports, but the paper does note that short-term extremes in temperatures have become more frequent on the continent.

Nor does that mean that all is well in Antarctica. Two scientific papers published in 2014 suggest the West Antarctic ice sheet has become dangerously weakened. One finds that a “large sector of the West Antarctic ice sheet … has passed the point of no return” and the other finds that the ice sheet has become sufficiently unstable to possibly collapse in as few as 200 years. That is a long time by ordinary human standards, but very brief in geological terms, and would add greatly to rising sea levels.

So what would a six-meter increase in ocean levels mean? More than 440,000 square miles (1.14 million square kilometers), where 375 million people, would go under water, according to Climate Central.

Annual global temperature anomalies from the 20th century average, since 1880 (graphic by U.S. National Oceanic and Atmospheric Administration)

The current path humanity is walking is to throw more greenhouse gases into the atmosphere. Current plans by political leaders to reduce greenhouse-gas emissions by 2050 and completely by 2100 are woefully inadequate, but even those goals will be difficult to achieve. The metabolism of capitalism, and all its incentives, is for more growth and thus more anthropogenic warming. And although reversing global warming is impossible without reducing consumption, that, too, is impossible under capitalism because a typical advanced capitalist country 60 to 70 percent of the economy is accounted for by household spending.

Because of the growth imperative of capitalism — the need to grow or die forces enterprises into never-ending innovations to cut costs — economic growth of 2.5 percent is necessary to maintain the unemployment rate where it is and “substantially stronger growth than that” is necessary for a rapid decrease, according to a former White House Council of Economic Advisers chair, Christina Romer. Capitalism will not guarantee new jobs for those made unemployed by closing down polluting industries, adding incentives to maintain them. “Free trade” agreements accelerate global warming because supply lines are stretched around the world and production is moved to the places with the lowest wages and weakest regulations. And as conventional sources of energy are depleted, more extreme measures are taken, including the exploitation of tar sands, adding still more greenhouse gases.

Our descendants are not likely to believe that short-term corporate profits and unsustainable consumption were a fair tradeoff for a world left much less habitable.

Sometimes you can’t win: More cold and snow thanks to global warming

If global warming is not simply warmer weather, but rather increasingly crazy weather, then this winter has given us ample evidence. An irony of global warming for eastern North America is it seems to be the one place that is getting colder and snowier winters thanks to global warming.

Curse you, Arctic oscillation! New York City just suffered through its coldest February since 1934, and its second-coldest month (any month) since then. Boston’s snow has been of historic proportions. And cities from Toronto and Buffalo to Bangor, Maine, recorded the coldest month in their recorded histories. On the other side of the continent, cities from Salt Lake City, Utah, to San Francisco and Seattle recorded their warmest winter months in history.

In Europe, 2014 was the hottest year on record, based on an analysis that examined temperatures going back to the 16th century, with global warming overwhelmingly the primary factor for such extremes. And, globally, 2014 was the hottest year on record, with the top 10 hottest years all occurring since 1998. There hasn’t been a year with an average global temperature below the 20th century’s average since 1976.

Average global temperatures have steadily risen for decades (Graphic by U.S. National Oceanic and Atmospheric Administration)

But nonetheless millions of people are suffering through an extraordinarily rough winter for a second consecutive year. And it may be that shrinking ice in the Arctic Ocean is a significant factor behind the extreme winters much of the Northern Hemisphere is experiencing. The Arctic oscillation is a measure of the relative strength of the jet stream, a high-level atmospheric wind that divides polar air from temperate air. When these winds are strong, the jet stream tends not to wander north and south, bottling up frigid air in the Arctic. When those winds slacken, the jet stream develops into a wave pattern, with large movements north and south.

Those high-level winds speed up and slacken based on the differences in barometric pressure between Arctic and mid-latitude regions; a related measure, the North Atlantic oscillation, is the difference between semi-permanent low pressure near Iceland and semi-permanent high pressure near the Azores Islands. When there are significant waves, or north/south amplitudes, unusually hot or cold weather is the result, depending on which side you are on. These patterns can lock into place for weeks or sometimes months, leading to persistent extreme weather.

What is causing these patterns? Research continues, but there is an increasing amount of evidence that a warming Arctic is the culprit. The Arctic is warming faster than the globe as a whole, and the polar ice cap is shrinking as a result, which in turns causes faster warming. Jeff Masters of the Weather Underground, in a discussion of a paper by Rutgers University scientist Jennifer Francis, summarized this theory:

“[T]he extra heat in the Arctic in fall and winter over the past decade had caused the Arctic atmosphere between the surface and 500 [millibars] (about 18,000 feet or 5,600 meters) to expand. As a result, the difference in temperature between the Arctic (60 – 80°N) and the mid-latitudes (30 – 50°N) fell significantly. It is this difference in temperature that drives the powerful jet stream winds that control much of our weather. The speed of fall and winter west-to-east upper-level winds at 500 [millibars] circling the North Pole decreased by 20% over the past decade, compared to the period 1948-2000, in response to the extra warmth in the Arctic.”

So although, overall, global warming means hotter temperatures, it doesn’t mean there will never be another cold day, and sometimes it leads to counter-intuitive results. Also, there should be some perspective here. Difficult as the sustained cold has been, it is the sort of weather than once was more common. It’s less common now precisely because Earth is getting warmer.

It was cool last year in Chicago, New Orleans and Tierra del Fuego, but not in too many other places.

It does not help that the corporate media lazily misuses the concept of “neutrality” to present a false controversy, as if there is still a debate as to whether global warming is happening, or if human activity is the cause if it is. The concept of media “neutrality” is easily exploited by denialist “think tanks” (and other lavishly funded corporate fronts) that pump out reports and provide spokespeople.

Denialist groups, well funded by energy companies and other multi-national corporations concerned with their short-term profits rather than the long-term health of the planet, seek to sew doubt among the public. The manufactured split in public opinion can then be leveraged to claim there is a “controversy,” dampening the resolve necessary to tackle a problem that will ultimately threaten the habitability of the planet. Consider that the reservoirs serving South America’s biggest city, São Paulo, are going dry and scientists believe the cause of the drought is Amazon deforestation.

The more you know, the more you realize you don’t know. Ignorance, however, is self-fulfilling — if you think you know everything, there is no need to learn anything. The global-warming denialists are following the playbook of religious fundamentalists who deny the reality of evolution by falsely claiming that a “controversy” exists in the face of overwhelming scientific evidence.

Those who deny evolution do no more than provide a source of amusement. The denial of a planet-wide crisis is something altogether different.