Monday, April 06, 2015
Warmists discover some real feedbacks
The feedback from increasing cloud that is central to their theory is very dubious. The best evidence is that clouds cause cooling, not warming. But there are various real climate feedbacks and they seem finally to have discovered some -- and put their "spin" on the discovery. I reproduce underneath the article below some comments by Profs. Robert Giegengack and Don Easterbrook
Scientists agree that an increase in atmospheric greenhouse gases causes the Earth’s temperature to rise, but they’ve also noticed that relationship seems to swing both ways: warmer temperatures also seem to correspond with an increase in greenhouse gases. But drawing conclusions about the nature of the relationship is tricky, because though scientists have seen a correlation, they haven’t been able to show causation.
Now, scientists believe they’ve untangled the relationship. In a paper published Monday in Nature Climate Change, researchers from the University of Exeter claim to have found direct evidence that as global temperatures rise, so does the atmospheric concentration of greenhouse gases, creating a positive feedback that in turn warms the Earth even more — basically, global warming creates more global warming.
“We discovered that not only does thickening the blanket of heat-trapping gases around our planet cause it to get warmer, but also, crucially, when it gets warmer this increases thickens the blanket of heat-trapping gases,” Tim Lenton, the paper’s author, told ThinkProgress, “so we have a process called a ‘positive feedback’ that amplifies changes in the Earth’s temperature.”
This isn’t the first time this relationship has been suggested. Scientists have previously used data from Antarctic ice cores to show that historic temperature rises were accompanied by spikes in global carbon dioxide levels, but other studies cast doubt on that timing, showing a lag of some thousand years.
While several models suggest a correlation between warming temperatures and an increase in greenhouse gas, Lenton’s team is the first to prove the relationship using direct evidence, taken from ice cores nearly one million years old.
The team — comprised of scientists from the University of Exeter, the Scripps Institution of Oceanography, and Wageningen University in the Netherlands — analyzed Antarctic ice core data from the end of ice age cycles 400,000 and 800,000 years ago. That ancient ice is important, because it offers an extremely large amount of historical global temperature and greenhouse gas concentration data, which the scientists were able to analyze to figure out how the two interact.
Combining historical data about temperature and greenhouse gas composition, the scientists used a mathematical approach known as Takens’ theorem to look at the relationship between the two. The approach, Lenton explained, is based on the idea that if one variable causes even a small change in the other, the more information you have about the first variable. The more information you have about the first variable, the better you should be able to predict the change in the second. Eventually the variables will converge, giving researchers an idea of how strong the first is in predicting change in the second.
“We find that if A and B are temperature and CO2 (or temperature and methane) we get strong reciprocal causality,” Lenton said, proving that warmer temperatures cause an increase in atmospheric greenhouse gases.
The findings provide even more support to the overwhelming evidence that humans are causing global warming by pumping greenhouse gases into the atmosphere. The surprise, Lenton explained, is that the findings also show that increasing temperature eventually increases greenhouse gases.
“It implies that we should expect the ‘Earth system’ to respond to anthropogenic global warming by amplifying it with the release of additional greenhouse gases,” Lenton said.
Though the study looks at historical data, Lenton acknowledges that current implications can’t be overlooked. “The Earth is a complex system containing many feedbacks, and they are strong enough to swing the planet between the depths of an ice age and a warm ‘interglacial’,” Lenton said.
The Earth is currently warming at a much faster rate than previous warming events, roughly ten times faster than ice-age-recovery warming, according to NASA. In 2013, atmospheric greenhouse gas hit a record high, and scientists warned that the Earth’s ability to store and mediate gas, through plants and oceans, might been approaching its saturation point.
We’re already seeing unexpected changes in the climate: the West Antarctic ice shelves, for instance, is melting at a much faster rate than scientists predicted. “As we meddle with the climate system now, driving it to hotter temperatures, we should expect the Earth to reply by amplifying the changes we are causing,” Lenton said.
Comment on the above by Prof. Robert Giegengack
"We" have known for a long time that the change in insolation represented by Milankovic variation is not adequate to bring about the change in temperature documented by the O-isotopes in the Antarctic ice cores.
From the time that the first ice-core data were published (~1980), students of climate change have acknowledged that, despite strong evidence that Milankovic cyclicity controls the timing of the glacial/non-glacial oscillation, the magnitude of temperature change recorded in the ice cores exceeds what could be expected from the Milankovic variations. Thus, positive feed-back processes have been invoked from day one. Those include:
1. albedo feedback: when it gets colder, glaciers advance at high latitudes/altitudes, and more incoming insolation is reflected to space by ice-covered surfaces; when it gets warmer, glaciers shrink, and exposed soil and open water absorb more insolation.
2. When the atmosphere is warmer, it holds more H2O vapor, the most effective greenhouse gas; as temperature falls, the capacity of the atmosphere to hold H2O as vapor declines
3. higher temperatures drive CO2 and other gases out of solution in sea water. When sea-water temperature declines, solubility of CO2 in sea water rises.
4. higher temperatures favor respiration of soil micro-organisms over photosynthetic drawdown of CO2; when temperatures fall, activity of soil micro-organisms is reduced, and photosynthetic drawdown of CO2 gets ahead.
5. higher temperatures thaw permafrost, releasing CH4 to the atmosphere. CH4 is also a greenhouse gas, but it quickly oxidizes to CO2 and H2O. We don't know the extent to which higher temperatures might release CH4 from methane hydrates on the continental shelves.
There may be other positive feedback processes, not yet identified.
This is not "news". The feedback processes were described in detail in the 1980s. They have operated in every glacial/non-glacial cycle represented in the Antarctic ice cores.
Prof. Don Easterbrook adds:
Ice cores leave little doubt that climatic warming ALWAYS precedes increases in atm CO2 and studies of shorter term (months/yrs) increases in CO2 following warming confirm the cause and effect of warming ----> increased atm CO2.
It is very clear from ice cores that ice ages are brought to a close abruptly by warming that precedes increased CO2 so CO2 is not involved in the warming. The weakness in this paper is that there is no evidence that CO2 causes more than insignificant warming.
Posted by John J. Ray (M.A.; Ph.D.).