Global Warming at work -- maybe

[Dogmudgeon]

It's mighty hot in California this week, and the drought in the South continues unbroken. Both of these weather stories made the news over the past few days, and would seem to give support to the Global Warming hypothesis.

Yet many meteorologists would say "no", and without political motivation. Weather is notoriouly fickle, and a few hot years in a short period -- say, from 1990 to 2003 -- isn't significant in the long run of things. But meteorologists readily admit that they really don't know. Climate science is still in its early years, hampered by the frustrating reality that it takes a long time to gather even a short run of data.

Many climate scientists -- and laypeople, like me -- are persuaded by climate models that show increasing warming, followed by a sudden climatic "mode change" to drastic cooling, perhaps even a full resumption of the ice age the Earth has been experiencing for the past two million years.

The transfer of heat in the North Atlantic ocean is under scrutiny as the "smoking gun" of global temperature regulation. According to the work of Wallace Broecker (Columbia/Lamont-Doherty) and Robert Gagosian (Woods Hole), the oceanic thermohaline (literally, "heat-salt") circulation in this area is the linchpin, and it has weakened in the past decade. As it weakens, the difference in temperatures between the northern and equatorial waters becomes greater -- the northern water becomes colder and less saline, and the equatorial water becomes warmer and more saline.

This is known as a "temperature gradient", and as many scientists know, large temperature gradients can indicate large amounts of energy at work -- or kept in check.

A similar temperature gradient has been forming between ground-level air and stratospheric air. The stratosphere's average temperature has been dropping since ground-level warming became established, from approximately -50F in the 1960s, to about -100F today. A relative temperature inversion may be forming world-wide. Temperature inversions at lower levels have produced locally deadly concentrations of smog on several occasions.

One hypothesis about climate change is as simple as it is frightening. These "imbalances" will eventually come to equilibrium when the energies required to maintain them weaken and collapse. The effects of that tipping point will a be quick slide on very real ice. This summer's blockbuster disaster movie, The Day After Tomorrow, will show Roland Emmerich's vision of such a climatic snap-back, which plunges the Earth into a full-bore ice age within a week. Other scientists take a more cautious view -- that the ice will return over the period of a decade, or, in Broecker's view, flicker on and off and finally back on over the period of a human lifetime. But none of the scenarios provide hope for much more than a major change for human life and history.

Dress warmly.

--bkl

[TexasProgresive]

1. Global weather is complex

The causes and the end results are something that we can only think about. It is likely that global warming will disrupt established weather patterns but that doesn't equate to every local warming. There is a new report that a north Atlantic current that is part of the Gulf Stream system is weakening. Some subscribe to the theory that excess warming will disrupt the Gulf Stream and lead to the freezing of Europe. Seems ironic that warming would make some places colder but the Earth continually attempts to balance itself.

Increasing fresh water melt from northern ice caps is decreasing the salinity of the North Atlantic. This fresh cold water tends to float instead of sinking which prevents the warmer water from the south from moving north. The circulation is halted and heat from the south never arrives. This scenario if true will lead to lower temperatures in Europe and perhaps a mini ice age.

Here in Texas we can probably expect n increase in an all ready hot clime as the Gulf continues to warm. But then, who knows?

On Edit: Some thing similar may be happening with the Japanese current which moderates the temperature of the west coast. If that current is slowed or stopped then Anchorage and Nome will freeze and the west coast may burn.

[Donkeyboy75]

2. Well, there's no doubt that warming is occurring.

Unfortunately, it's difficult to separate all of the variables and tease out what's artificial and what isn't. After all, most of the continental U.S. was tropical rain forest millions of years ago.

There's an article in the current Nature that has set up the most sophisticated model so far to deal with this, and the good news is that it is geared towards policymakers. Nature and Science are both paying a lot of attention to this issue, and it will start to be impossible for policymakers to ignore.

[Viking12]

4. DB75

Browsing the Table of Contents, I didn't see any articles on Climate Modeling in the April 22 Nature. It could be that the title isn't reflective of the content. Do you have a title or pages, I would like to read it.

[Donkeyboy75]

5. That's because it's in Science.

:dunce:

Sorry about that, I must've gotten the two crossed in my sleep deprived brain last night. Anyway, it's on page 571 of the current Science. The most gripping conclusion is in the abstract:


Analyses with a simple integrated assessment model found that, under midrange assumptions, endogenously calculated, optimal climate policy controls can reduce the probability of dangerous anthropogenic interference from 45% under minimal controls to near zero.

Enjoy :hi:

[Viking12]

7. I found it...

thanks for the reply..


Probabilistic Integrated Assessment of "Dangerous" Climate Change
Michael D. Mastrandrea and Stephen H. Schneider
Abstract:
Climate policy decisions are being made despite layers of uncertainty. Such decisions directly influence the potential for "dangerous anthropogenic interference with the climate system." We mapped a metric for this concept, based on Intergovernmental Panel on Climate Change assessment of climate impacts, onto probability distributions of future climate change produced from uncertainty in key parameters of the coupled social-natural system—climate sensitivity, climate damages, and discount rate. Analyses with a simple integrated assessment model found that, under midrange assumptions, endogenously calculated, optimal climate policy controls can reduce the probability of dangerous anthropogenic interference from 45% under minimal controls to near zero.

I hope to find some time tonight to give it a complete read. :)

[Dogmudgeon]

3. The Issue of Complexity

Complexity is usually cited as the reason for foot-dragging on important issues. The need for someone or something to blame is so strong that, until the "smoking gun" is found, the Powers That Be are content to Let It Be.

But it is possible, even before blame can be established, to show that a system is changing rapidly. This is happening to the Earth's climate and oceans right now. The "anomalies" -- deviations from the norm -- being recorded by both meteorologists and oceanographers are the largest ever seen. And not only that, the anomalies are happening again and again, year after year, with few or no gaps.

These climatic anomalies only got going in the early 1990s. And they really are historic. Several countries have weather records that reach back centuries, and show nothing like we've been seeing recently. Last year the European summer was so hot that thousands of people died there -- I believe that the previous summer that even approached that level was in the 1850s.

Also, some of the aggregate data are so small that laypeople -- and even many scientists -- fail to appreciate their significance. The "height" of the last ice age, called the Würm Glaciation in Europe (Wisconsonian in North America), brought world-wide temperatures down by about 8C. Of course, the temperature drop was much greater in subarctic Europe and profound over areas covered by ice.

Right now, I think we're at the point where discussing whether human industry caused all of it, or part of it, or none of it, is absurd. It is coming, and we don't know quite what It may be, but caution dictates that we have an emergency plan or two in place. Unlike the upcoming movie The Day After Tomorrow, we are likely to have more than a month or so to prepare. Even in the most drastic scenarios, a climate flip-flop will still take a few years to set in.

But the current practice of making fun of people calling for caution is ill-advised. This holds true for any important issue, whether it's climate change, oil supply contraction, asteroid and cometary impacts, state assaults on civil liberties, or infectious disease.

By early August, I can imagine that hundreds of tongue-in-cheek articles citing "skeptical" scientists will be running in the popular press taking issue with the movie. After all, it's being filmed as a disaster movie, not a scientific travelogue. But embedded within the "bwa-ha" throng will be hundreds of voices of Industry supported by millions of dollars to convince the world that Nothing Is Wrong. And all those bwa-has add up -- we've blissfully ignored the prospect of a real energy crisis for 30 years since the one that resulted from the political reaction of the Saud family. A crisis coming from natural sources will not be so forgiving of our complacency.

Well, something is wrong. Careful observation and a suitable "Plan B" should be the minimum preparations we make. Better to be well-prepared and surprised than to be unprepared and shocked.

--bkl

[jpak]

6. Smoking gun??? I thought this was old news...

Richard A. Kerr (2001) It's Official: Humans Are Behind Most of Global Warming. Science Vol. 291 pp 566

SUMMARY: The United Nations-sponsored Intergovernmental Panel on Climate Change officially declared early this week that "most of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations." The panel was vaguer than ever, though, about how bad things could get by the end of the century. At a minimum, the world will warm more than twice as much in the coming century as it did in the past one, the panel concluded, but it could warm 10 times as much.

T. P. Barnett, D. W. Pierce, R. Schnur (2001). Detection of Anthropogenic Climate Change in the World's Oceans. Science Vol. 292: pp 270-274.

ABSTRACT: Large-scale increases in the heat content of the world's oceans have been observed to occur over the last 45 years. The horizontal and temporal character of these changes has been closely replicated by the state-of-the-art Parallel Climate Model (PCM) forced by observed and estimated anthropogenic gases. Application of optimal detection methodology shows that the model-produced signals are indistinguishable from the observations at the 0.05 confidence level. Further, the chances of either the anthropogenic or observed signals being produced by the PCM as a result of natural, internal forcing alone are less than 5%. This suggests that the observed ocean heat-content changes are consistent with those expected from anthropogenic forcing, which broadens the basis for claims that an anthropogenic signal has been detected in the global climate system. Additionally, the requirement that modeled ocean heat uptakes match observations puts a strong, new constraint on anthropogenically forced climate models. It is unknown if the current generation of climate models, other than the PCM, meet this constraint.

S. Levitus, J. I. Antonov, J. Wang, T. L. Delworth, K. W. Dixon, and A. J. Broccoli (2001) Anthropogenic Warming of Earth's Climate System. Science Vol 292: pp 267-270.

ABSTRACT
We compared the temporal variability of the heat content of the world ocean, of the global atmosphere, and of components of Earth's cryosphere during the latter half of the 20th century. Each component has increased its heat content (the atmosphere and the ocean) or exhibited melting (the cryosphere). The estimated increase of observed global ocean heat content (over the depth range from 0 to 3000 meters) between the 1950s and 1990s is at least one order of magnitude larger than the increase in heat content of any other component. Simulation results using an atmosphere-ocean general circulation model that includes estimates of the radiative effects of observed temporal variations in greenhouse gases, sulfate aerosols, solar irradiance, and volcanic aerosols over the past century agree with our observation-based estimate of the increase in ocean heat content. The results we present suggest that the observed increase in ocean heat content may largely be due to the increase of anthropogenic gases in Earth's atmosphere.

J. E. Harries, H. E. Brindley, P. J. Sagoo, R. J. Bantges (2001). Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997. Nature Vol. 410 pp 355 - 357

ABSTRACT: The evolution of the Earth's climate has been extensively studied, and a strong link between increases in surface temperatures and greenhouse gases has been established. But this relationship is complicated by several feedback processes—most importantly the hydrological cycle—that are not well understood. Changes in the Earth's greenhouse effect can be detected from variations in the spectrum of outgoing longwave radiation, which is a measure of how the Earth cools to space and carries the imprint of the gases that are responsible for the greenhouse effect. Here we analyse the difference between the spectra of the outgoing longwave radiation of the Earth as measured by orbiting spacecraft in 1970 and 1997. We find differences in the spectra that point to long-term changes in atmospheric CH4, CO2 and O3 as well as CFC-11 and CFC-12. Our results provide direct experimental evidence for a significant increase in the Earth's greenhouse effect that is consistent with concerns over radiative forcing of climate.