Comments
Natural Climate Shifts: Swanson v Tsonis
Tsonis et al have published 3 interesting studies (2007, 2009, 2009) on how natural climate cycles could account for the climate/temperature shifts in the 20th and 21st centuries. The main authors Anastasios Tsonis and Kyle Swanson appear to have slightly conflicting opinions in media articles as to the significance of their work to the case for man-made global warming.
A Discovery News article quoting Swanson on 2nd March 2009 is entitled:
Warming might be on hold, study finds, Authors sense hibernation, but warn of ‘explosive’ rise later
Swanson is quoted as saying (excerpts):
Earth’s climate continues to confound scientists. Following a 30-year trend of warming, global temperatures have flatlined since 2001 despite rising greenhouse gas concentrations, and a heat surplus that should have cranked up the planetary thermostat.
“This is nothing like anything we’ve seen since 1950,” Kyle Swanson of the University of Wisconsin-Milwaukee said. “Cooling events since then had firm causes, like eruptions or large-magnitude La Ninas. This current cooling doesn’t have one.”
Instead, Swanson and colleague Anastasios Tsonis think a series of climate processes have aligned, conspiring to chill the climate. In 1997 and 1998, the tropical Pacific Ocean warmed rapidly in what Swanson called a “super El Nino event.” It sent a shock wave through the oceans and atmosphere, jarring their circulation patterns into unison.
How does this square with temperature records from 2005-2007, by some measurements among the warmest years on record? When added up with the other four years since 2001, Swanson said the overall trend is flat, even though temperatures should have gone up by 0.2 degrees Centigrade (0.36 degrees Fahrenheit) during that time.
“When the climate kicks back out of this state, we’ll have explosive warming,” Swanson said. “Thirty years of greenhouse gas radiative forcing will still be there and then bang, the warming will return and be very aggressive.”
Meanwhile, on 15th March 2009, Tsonis is qouted in a separate article for ABC’s wisn.com :
in which Tsonis is quoted as saying (excerpt):
Now the question is how has warming slowed and how much influence does human activity have?
“But if we don’t understand what is natural, I don’t think we can say much about what the humans are doing. So our interest is to understand — first the natural variability of climate — and then take it from there. So we were very excited when we realized a lot of changes in the past century from warmer to cooler and then back to warmer were all natural,” Tsonis said.
Tsonis said he thinks the current trend of steady or even cooling earth temps may last a couple of decades or until the next climate shift occurs.
More recently Swanson has written a guest post for the ‘Real Climate’ ‘consensus pushing’ weblog on 12th July 2009:
Warming, interrupted: Much ado about natural variability
Roger Pielke Jr has an interesting take on this on his blog:
Two Decades of No Warming, Consistent with…..
“Over at Real Climate they are busy giving climate skeptics reason to cheer:
We hypothesize that the established pre-1998 trend is the true forced warming signal, and that the climate system effectively overshot this signal in response to the 1997/98 El Niño. This overshoot is in the process of radiatively dissipating, and the climate will return to its earlier defined, greenhouse gas-forced warming signal. If this hypothesis is correct, the era of consistent record-breaking global mean temperatures will not resume until roughly 2020.
Imagine, twenty-two or more years (1998 to ~2020) of no new global temperature record. What would that do to the debate?
Real Climate does say something very smart in the piece (emphasis added):
Nature (with hopefully some constructive input from humans) will decide the global warming question based upon climate sensitivity, net radiative forcing, and oceanic storage of heat, not on the type of multi-decadal time scale variability we are discussing here. However, this apparent impulsive behavior explicitly highlights the fact that humanity is poking a complex, nonlinear system with GHG forcing – and that there are no guarantees to how the climate may respond.
As I’ve argued many times, uncertainty is a far batter reason for justifying action than overhyped claims to certainty, or worse, claims that any possible behavior of the climate system is somehow “consistent with” expectations. Policy makers and the public can handle uncertainty, its the nonsense they have trouble with.”
July 17th, 2009 at 1:45 am
Why cant’t so called scientist look at the big picture. We are currently in a almost 11,000 year old interglacial period; 100,000 years of expanding glaciers, 10,000 to 15,000 years of relative warm. The differential between the 2 periods is as much as 10 degrees centigrade. We are on declining slope of our current interglacial period that mankind was fortunate enough to live in. In the last 2,000 years we have oscillated between warm and cooler periods (~2 degrees difference) lasting ~400 years: Roman warm period, the cooler Dark Ages, the Medievil warm period, the Little Ice age, and finally the modern warm period. In 1715, the world came out of the Mauder Minimum, the coldest period of the Little Ice age that lasted 70 years. Thus for the last almost 300 years, we have been warming at a gentle, non threatening rate. Superimposed on this gentle rate is ~60 year oscillation that can mean as much as a change of 0.5 degrees; we warming for 30 years, then cooling. 1975 – 2001 was the warming portion of the 60 years cycle; 1947 – 1975 was cooling; 2001 – ? is again cooling. Soon, the modern warm period will be in its decling phase and a longer period of cooling of 400 years will occur. Of course this ignores the deadly possibility that we may soon enter a 100,000 years of expanding ice. CO2 is a trivial player in this scheme; look to the sun for your cause of temperature change. One final thought, cold is deadly; warm is life giving.
July 17th, 2009 at 2:31 am
Well said!