Posted 3 years ago on March 18, 2014, 5:40 p.m. EST by LeoYo
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Abrupt Climate Change: No Bioperturbation
Tuesday, 18 March 2014 09:07
By Bruce Melton, Truthout | News Analysis
Today, we are burning fossil carbon one million times faster than it was naturally put in the ground, and carbon dioxide is increasing 14,000 times faster than anytime in the last 610,000 years (1,2). Climate is now changing faster than it has during any other time in 65 million years - 100 times faster than the Paleocene/Eocene extinction event 56 million years ago see here.(3) However, "climate change" is not the most critical issue facing society today; abrupt climate change is. Climate scientists now have the knowledge necessary to guide us beyond existing climate pollution policy. New policy needs to focus on abrupt climate change, not the relatively slow changes we see in climate models of our future. The social, economic and biological disruptive potential of abrupt climate change is far greater than that of the gradual climate change present policy is predicated upon.
Over about the last 100,000 years, the world has seen about 20 abrupt climate changes, averaging 9 to 14 degrees, including in Greenland, where the temperature changed up to 25 to 35 degrees. These abrupt climate changes happen 10 to 100 times faster than the climate change projections we have all come to know and love. Mostly they happened in several decades or less, but one of the biggest changes happened in just a few years. (4)
The evidence of these abrupt changes is clear in the highly accurate findings from ancient preserved air in ice sheets. They were likely all related to feedbacks and thresholds or tipping points. There are many different kinds of feedbacks and tipping points and the science is still unclear on many of them. Feedbacks are things like the snow and ice feedback loop: snow and ice reflect up to 90 percent of the sun's energy back into space harmlessly as light, while ocean, rocks, soil, vegetation and etc. reflect only 10 percent back into space, and the rest is absorbed and turned into heat energy that gets trapped by the greenhouse effect. The trapped energy creates more warming, that melts more snow and ice, that absorbs even more energy, changing it into heat, and the loop continues until all the snow and ice are gone.
Tipping points are a little bit more difficult to describe in environmental systems, but can easily be described in other ways. A canoe has a tipping point, beyond which a dry lovely day on the water turns into something quite different. Environmental systems behave in a similar manner. We can dump a lot of water pollution into our lakes and rivers, and nothing major seems to happen. Degradation occurs, but the lake or river generally continues to behave like a lake or river until the pollution levels reach a critical point. Then, as when one leans over just a little too far in a canoe, an algae bloom happens and the lake or river turns green or brown overnight and gets really smelly and bad tasting. This is an ecosystem tipping point. Pollution levels (nutrients from wastewater treatment plants, urban stormwater runoff agriculture, etc.) accumulate over time to a sufficiently high level that finally, an algae population explosion occurs. Then a really devastating thing sometimes occurs if the tipping point is really critical. All the algae die, sink to the bottom and decompose simultaneously. The decomposition uses up all the oxygen in the water and there is a big fish kill on top of the stinky smelly unsightly algal bloom.
Our global environment is no different from a lake or river or even a canoe. Some of these 20 or so abrupt changes happened in direct response to tipping points that preceded them, like a shutdown of the North Atlantic portion of the Gulf Stream. Some of them happened because one or more feedbacks went out of control. Pinning down exact causes of the abrupt changes, however, remains a difficult task.
Unearthing the Evidence
Abrupt climate change wasn't really a recognized phenomenon until about 20 years ago. Strong evidence of abrupt temperature changes had been found in the 1960s in Greenland ice cores, but they were poorly understood and considered anomalies at the time. Climate change science was dominated by sediment cores from oceans and lakes and slow, glacially paced changes of the 100,000-year cycles of our climate as Earth's tilt and orbit changed around the sun. As time passed, the early evidence of abrupt change was found again and again in subsequent ice cores. Even in Antarctica, these same abrupt signals were found.
2014 0317modo3 Bubbles of ancient air preserved in Greenland ice. (Photo: Bruce Melton)
Those first records of abrupt climate change from the 1960s at Camp Century were found in ice cores from a WWII nuclear base in the middle of the Greenland Ice Sheet. Camp Century was chosen as one of the first places to drill ice because it was an existing station in a very hostile environment. The Greenland Ice Sheet is over two miles thick and 11,000 feet high. The ice cores seemed to show radical climate jumps in the clearly visible annual layers of snow, in oxygen and methane in the preserved ancient air and dust that increased and decreased dramatically according to temperature.
Over the next two decades and continued ice core drilling, the same signs of abrupt changes were seen, and some confidence began to emerge about the validity of this amazing storehouse of evidence. It was not until the early 1990s, though, that the story became clear. Two identical ice cores were drilled in one of the most stable parts of the ice sheet. The cores were identical down to 100,000 years ago, then close to bedrock, the annual layers became warped and folded. Above the level of ice at 100,000 years ago, the ice cores matched identically. The same volcanic eruptions from across the world were represented by characteristic ash from the different eruptions. Even the same dust from Siberia during really cold dry periods was found in the different ice cores. These abrupt changes were real and they were radical. Why then did sediment cores not reveal abrupt changes?
Universally, these abrupt climate changes dwarf climate change projected by our world's scientific institutions in their summaries of climate change projections
The reason was biopertubation. Bioperturbation is what happens to sediments when worms eat through organic material on the bottom of a lake or ocean. Dozens and even hundreds of years of sediment deposition per inch are mixed and remixed by the worms. It happens to almost all sediments everywhere. The best resolution in sediments at the time was really a century or more or even thousands of years. The abrupt nature of actual changes in the annual sediment layers was simply wiped out, or eaten up. Then we began to learn of areas of the globe where biopertubation did not exist.
A few areas of the ocean were identified that were stagnant and devoid of oxygen. Worms can't live without oxygen and in these areas there is no bioperturbation. The same abrupt climate jumps as were found in Greenland were now plain to see. We have also found the same evidence in the annual layers of stalagmites and other cave formations.
It took another decade for science to catch up, but what we know now is that Earth's climate normally changes through abrupt shifts. Climate change is mostly not a slow, glacially paced thing. The changes are fast and violent and leave ecosystems shredded in their wake. They start out slowly, but then a threshold is crossed, and the temperature jumps up or down far more radically than the slow and modest warming projected by almost all climate change models today. Universally, these abrupt climate changes dwarf climate change projected by our world's scientific institutions in their summaries of climate change projections.