Post by marchesarosa on Dec 14, 2012 17:19:12 GMT 1
Our Chaotic Climate System
December 14th, 2012 by Prof Roy W. Spencer, Ph. D.
Over the last quarter century, mainstream climate science has changed dramatically, from a paradigm where climate changes naturally to one where climate forever remains the same unless humans meddle with it.
The reasons for this paradigm shift are clearly not based on science. Sure, you can always analyze some dataset in such a way that it gives the appearance of climate stasis (e.g. the hockey stick), but there is plenty of published research over the last 50 years supporting the view that climate changes naturally, and on all time scales…decadal, centennial, millennial, etc.
The claim that the Medieval Warm Period or Little Ice Age were only regional in extent is countered with considerable published evidence to the contrary. Besides…why is it that the pundits who claim these historic events were only regional in extent are the same people who place global significance on a U.S. drought or a heat wave in France? Hmmm?
No, the reasons for this paradigm shift are mostly political. Scientists play along for a variety of reasons which would take a series of blog posts to cover.
But they have been pretty successful at convincing the science-savvy public that climate will only change when we fire up our SUV, or turn on our incandescent light bulbs. The scientists say things like, “We tried putting natural forcings in our models, but we can get the models to produce the observed warming only when we include anthropogenic greenhouse gas emissions.”
Well, they only put in a few forcings which they know about: total solar irradiance changes, ozone depletion, and maybe a couple others.
But what about changes which are not “forced”?
Our Chaotic Climate System
Chaos theory was originally developed by Ed Lorenz during early experiments with computerized weather prediction models, the forerunners of today’s climate models. Lorenz found that, for example, even tiny changes in the initial state of the atmosphere can completely change how weather patterns evolve in the coming weeks. Chaos is what limits the predictability of weather to 10 days or so.
Chaotic behavior is a characteristic of most nonlinear dynamical systems, that is, systems which evolve over time and are governed by rather complex physical processes. We usually think of chaos in the atmosphere operating on time scales of days to weeks.
But the ocean is also a nonlinear dynamical system. And it has time scales ranging from years up to hundreds or even thousands of years…time scales we associate with climate change.
El Nino and La Nina can, for example, be thought of as a chaotic fluctuation in the climate system. Like the famous butterfly-shaped Lorenz Attractor, El Nino and La Nina are the two wings of the butterfly, and the climate system during Northern Hemisphere winter tends to alternate between El Nino and La Nina, sometimes getting “stuck” in a multi-year pattern of more frequent El Ninos or La Ninas.
Now, while El Nino and La Nina are the best known (and most frequently occurring) ocean-based climate phenomenon, what other longer-term modes of climate variability might there be which are “unforced”?) By unforced, I mean they are not caused by some external forcing mechanism (like the sun), but are just the natural results of how the system varies all by itself.) Well, we really don’t know, partly because so little research is funded to study the problem.
But How Can Chaos Cause “Global Warming”?
It is my belief that most climate variability and even climate change could simply be the result of chaos in the climate system. But how would changing ocean and atmospheric circulation patterns cause “global warming”?
One potential mechanism is through the impact of those circulation changes on cloud formation.
Clouds are the Earth’s natural sunshade, and very small (but persistent) changes in cloud cover can cause either warming or cooling trends. I know that scientists like Trenberth and Dessler like to claim that “clouds don’t cause climate change”…well, chaotic changes in ocean and atmospheric circulation patterns can change clouds, and so in that sense clouds act as an intermediary. Of course clouds don’t change all by themselves, which is how some people disingenuously characterize my position on this.
Unfortunately, our long-term measurements of global cloud cover are not yet good enough to determine with a high level of confidence just how much recent warming was caused by climate chaos. Our experiments with a simple 1D energy budget model suggests that more frequent El Ninos since the late 1970s caused some of the warming we have seen (a position also taken by Bob Tisdale), but just how much of the warming remains uncertain.
Part of the El Nino warming seems to be through reduced cloud cover, which precedes peak warming by 7 to 9 months. But it is also through a decrease in the rate at which the ocean mixes heat vertically. Chaotic changes in ocean mixing alone can cause global warming or cooling, even without any cloud changes, the result of the fact that most of the depth of the ocean is very cold, and only the near-surface is relatively warm. If the ocean was vertically uniform in temperature, changes in ocean mixing would have little effect on climate.
This is the basis for Trenberth’s “missing heat” argument. If recent warming has indeed been caused by our greenhouse gas emissions, but there has also been an increase in the rate of overturning of the oceans, then surface warming will be reduced as colder deep water is brought to the surface and the deep ocean is slightly warmed from the warm surface waters being mixed deeper than usual. Unfortunately, since the oceans are SO deep, the deep ocean warming we would be talking about verges on being unmeasurable…thousandths of a degree.
While such a “missing heat” explanation for a lack of recent warming is theoretically possible, I find it rather unsatisfying basing an unwavering belief in eventual catastrophic global warming on a deep-ocean mechanism so weak we can’t even measure it. Larger changes in individual ocean basins might be measurable, but it is the global average deep-ocean temperature that we need to know very accurately.
The Need for Natural Climate Change Research
This issue of natural mechanisms of climate change is so important it boggles my mind that the U.S. Government has had almost zero interest in funding it. But I don’t see how we will ever confidently determine just how much of recent warming is human-induced without determining how much was natural.
If, say, 50% of the warming in the last 50 to 100 years has been natural, then this profoundly impacts our projections of human-caused warming in the future, slashing them by about 50%.
In my talks to groups around the country over the years, I find widespread public support for the idea that climate does indeed change naturally. For the scientists who the public supports financially to largely ignore the issue, I fear that there will eventually be a public backlash which will end up hurting taxpayer support of climate research.
Unless they start behaving a little more like objective scientists, I predict that global warming researchers are living on borrowed time.
www.drroyspencer.com/2012/12/our-chaotic-climate-system/#comments
