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Bob Ryan on Global Warming, Part 5

Is our climate changing?

By BOB RYAN

Updated 8:33 AM EDT, Mon, Mar 9, 2009

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NATURAL OR MAN MADE?

Haze and pollution over China. Shanghai is on the right somewhere under the gray cloud. (Courtesy NASA)

Haze over mid-Atlantic as a summer cool front clears New England (Courtesy NASA)

Dust storm over Egypt and smoke over Nile Delta January 2003 (Courtesy NASA)

What we see is that both nature and humans put material in the atmosphere that can change the transparency of the air and the reflectivity, or the “albedo,” of the Earth and have an effect on the temperature of the atmosphere and Earth.

Indeed some scientists believe that increases in carbon dioxide in the late 1960s and 1970s, which would have a warming effect on the atmosphere, were balanced by the reflective cooling properties of pollution like we see in the middle picture above. China now is adding more carbon dioxide to the atmosphere than the United States. But as we observe above, it is also adding haze and pollution -- a so-called “brown cloud” -- which may be countering the warming that theory says should be occurring because of increasing greenhouse gases carbon dioxide and methane.

And it’s not just the atmosphere and what is in it that affects our weather and climate.

Ideas, Hypothesis, Theories and Tests

So, I hope you are still with me. We have looked at how science works, if you will. We’ve made observations of everything from population to gases, temperature, volcanoes, the Sun, haze, the oceans, weather and climate; and now we’ll take those observations and, like the Swedish chemist, Svante Arrhenius and the later work and observations of British engineer/amateur meteorologist Guy Callendar (see “The Callendar Effect”), study and interpret observations and form an idea -- a scientific hypothesis.

The idea: The hypothesis is that increasing amounts of carbon dioxide that are released from burning fossil fuels will (because we have an idea of the theory of “the greenhouse effect”) lead to an increase of the average temperature of the air/atmosphere.

So how will we test this idea, this hypothesis?

Since we now have the observations and general scientific understanding of the physics of the atmosphere, ocean and land (things such as evaporation, soil moisture, motion of air, solar radiation etc.) and mathematical tools (equations -- the language of science) and methods and tools (powerful computers) to solve the complex mathematics, we will form a mathematical/scientific “model” of the atmosphere/ocean/land system and see how well it reproduces or simulates the behavior of the weather and climate system.

One question we first have to answer: Does our model produce anything similar to what we observe? If we start with observations in the past (let’s say 1950) does it give us reasonable answers about the climate we observe today? Can our model be tested by other scientists? If so, then we have a “theory” -- an idea that is testable by others -- and if apparently fundamentally correct, may be verified or adjusted as the theory undergoes repeatable trial and error?

Remember that guy Newton under the tree? We test his theory of universal gravity every day, and so far the theory is verified. But, is it a “fact?”

So how are these “models” (called general circulation models or GCMs) doing and what do they show? Here is one of the better examples that I showed before.

This graph of the model results shows how observations of global temperatures do generally agree with the hypothesis of increasing anthropogenic concentrations of carbon dioxide and other greenhouse gases and observations of increasing global temperatures.

The wide blue and red bands also show the uncertainty (this is important ... more later) of the results. Again, there is the thought/theory that in the 70s, with better air pollution controls, the cooling effect of human-produced pollution and hazes were reduced and the offsetting warming effects from greenhouse gases became more important.

Is a similar thing happening now with China and Asia producing both greenhouse gases but also “brown clouds?” How do we fit that into the models and is it good or bad? Do we want “dirty air” and the resultant health risks to offset global warming by increasing carbon dioxide concentrations in the atmosphere? I promised no “policy,” but these are important questions to consider? What is the uncertainty? Remember this?

Before we go much farther, you should know that “uncertainty” in science does not mean “unknown.” Every measurement you or I make, everything we do (of course except death and taxes) has some uncertainty. The history of certainty and uncertainty in science is quite interesting (http://books.nap.edu/catalog.php?record_id=10248).

The Intergovernmental Panel on Climate Change (IPCC), which is the international group of hundreds of the world’s leading research scientists (and lightning rod for political and some scientific criticism), regularly issues peer reviewed (reviewed by scientists working in the same field) reports on the very latest thinking and research results for various future global warming possibilities. Its most recent report shows this projection of average global (remember regional and local averages may be quite different) temperatures under various social/energy assumptions in the coming years for our children, grandchildren, great grandchildren etc.

The green region shows the projection based on a likely pattern with continued world population growth under current social environments and yet advances in new energy sources and conservation. The blue region assumes rapid improvements in education worldwide and rapid changes in alternative energy sources to reduce dependence on fossil fuels source. The color bands indicate a 70 percent probability that the projections/forecasts will be within that range. Both projections arrive at projections of a warmer world. Warmer (remember these are global averages) of anywhere from a bit over +2° to +6° F. by 2100.

A joint program at MIT in Cambridge, Mass. has been looking at various global studies and projects and presents another interesting picture of what the current research in climate change is projecting as possible temperature change by 2100.

“The wheel below depicts the MIT Joint Program's estimation of the range of probability of potential global warming over the next hundred years, assuming a scenario in which "no policy" action is taken to try to curb the global emissions of greenhouse gases. The face of the wheel is divided into six slices, with the size of each slice representing the estimated probability of the temperature change in the year 2100 falling within that range. The size of the slice for greater than 7 degrees Celsius warming (shown in red) has a probability of 9%. Or, if stated in another way, that probability has the same likelihood as the "odds" of (about) 1 chance in 11. The slice representing the smallest predicted change, less than 3°C (shown in blue), has a probability of less than 1% (1 in 100 odds). The median value, that level where there is a 50% chance of falling above or below (even odds) is 5.1°C. The other areas of the wheel have likelihoods of occurring: 3 to 4°C, 12% (about 1 in 8); 4 to 5°C, 30% (almost 1 in 3 odds); 5 to 6 °C, 33% (1 in 3 odds); 6 to 7 °C, 15% (about 1 in 7 odds).”

Courtesy The MIT Joint Program on Science and Policy of Global Change

Remember Two Things

These temperatures are shown in Celsius, the metric system measure of temperature that most of the world uses. For our Fahrenheit system, you can roughly multiply these temperature changes by 2. And what is the other “remember this?” Remember the uncertainty. These both are probable projections.

If you and I are reading the very latest “scientific finding” especially in some report by any group that may have a more political rather than science agenda and it doesn’t tell us about the uncertainties of the uncertain projections, we have to be skeptical that it is really useful.

In contrast, the graphical examples above are very useful studies and how we should all think about some of the projections of my science.

Is it useful for you to think as “probable” change? If we try to forecast climate with the best science and probabilistic tools we have now, and find there is a 2 percent to 6 percent possibility that the future global temperature will increase by less than 1° by 2100 and a 2 percent to 6 percent chance it may increase by 8-10° F, but a 60 percent chance the global temperature will increase 3°- 6° F, what do we do?

The decisions to follow are too important to have all of us not involved and also have some understanding of the science, the uncertainties and the probabilities. The “stuff” before the politics ... almost.

The end is in sight Scarlett ... tomorrow.