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a handsome mathematician and scientist. These cycles are known as Milankovitch cycles.
You might start with the story of climate change. There are several non-human caused agents of climate change.
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So those were the main players in effect before humans came along, about two
million years ago or so. Then, for a long time after that, humans didn't cause
any trouble, because they weren't very numerous, and hadn't invented so much
cool technology. But in the mid-1700s, the industrial revolution kicked up and
humans began to belch carbon into the air in exchange for the energy to do
really powerful things:
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Using wood or coal, we began powering a new civilization, where people began moving about the Earth at great speeds, building huge cities, empowering agriculture, so that more people could be fed by fewer. It was a dramatic shift. Even as late as 1952 London was so famously polluted by coal exhaust from its power plants that "The Great Smog of 1952" took thousands of lives. Today it's Beijing that is famously smoggy with coal pollution. We haven't learned much in 60 years. |
With the oil boom in the late 1800s, and gasoline, soon people everywhere were purchasing their own private vehicles for transportation. This created a whole new source for carbon to be pumped into the atmosphere, as we continue to do today.
Early on in the game people began to suspect that all this might not be an entirely good thing. So for a short chronology of the party poopers, let's begin with Joseph Fourier, who in about 1824 informed the world that it's our atmosphere that "keeps the heat in" from the sun, and allows our planet to retain life-giving warmth.
Once we have an atmosphere, it's important to know what its constituents are: the wrong molecules in the wrong quantities, and you could end up like Venus (460 degrees C), covered in carbon dioxide. We're fortunate in having plenty of oxygen and nitrogen, in addition to CO2 and other gases, and we're able to survive just fine with a pleasant annual global temperature of around 14 degrees C.
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Then in 1861, John Tyndall (Irish, 1820-1893) presented scientific evidence that carbon in the atmosphere would retain infrared heat -- the kind generated when the Earth heats up under the influence of the sun's rays. |
For awhile people thought that increasing carbon in the atmosphere might be a good thing: the more the CO2, the more the plants are happy, right?
| The most famous such scientist was Svante Arrhenius (Swedish, 1859-1927), who was the first to estimate the impact of doubling the concentration of CO2 in our atmosphere (over 100 years ago -- he thought that doubling CO2 would raise temperatures about 5-6oC). Ironically, he thought that the increase in CO2 would have a generally positive impact on Earth -- warmer average temperatures sounded good, and CO2 is good for plants, after all. |
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Average global surface temperature has indeed been rising in recent decades, as Arrhenius foresaw:
Science has now shown that the warming Arrhenius anticipated will not necessarily be good news for humanity. Impacts such as ocean acidification pose significant threats to the bottom of our food chain. And average temperature isn't necessarily the thing to watch: variation in temperature and climate is increasing due to feedbacks, such as increasingly warm air holding more moisture, leading to more massive storms; increasing ocean temperatures lead to larger hurricanes; etc. We're getting extremes in weather more frequently than previously expected, with astonishing impacts on economies and in terms of human suffering (not to mention the suffering of other species, which we can generally hold blameless in this mess!).
Gilbert Plass (Canadian, 1920-2004) wrote a 1956 paper in the American Scientist that revived the fading CO2 theory of climate change, and in the late 1950s a scientist named Charles David Keeling began to record the rise of carbon in our atmosphere. We've watched it rise steadily since then (with rhythmic pulsations brought on by our global forests breathing CO2 in and out! "One breath per year", as James Hansen has said):
By the 1980s scientists had seen enough to become concerned, and to put the big picture together. Carl Sagan, the once famous astronomer and popularizer of science, gave testimony before the United States House of Representatives in 1984, in which he laid out the situation as he understood it (and better than I do here, so I will quote him at length):
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So now let's say something about greenhouse effect. In a very simple way,
what happens in the greenhouse effect is something like this.... [C]onsider a
planet with air, like our own, which is clearly transparent -- except in Los
Angeles -- to sunlight. So visible light from the Sun comes through the
atmosphere and strikes the surface and ... warms it up. The surface, like every
other object in the universe that is not at absolute zero, radiates and at the
temperatures of the surface of the Earth, it radiates mainly in the infrared
part of the spectrum, radiation that is longer wave than the red part of the
visible spectrum. You do not directly sense infrared radiation, sometimes
called heat radiation, but it sure is there.
What happens is, a kind of equilibrium is established so that the amount of sunlight coming in from the Sun that is absorbed by the planet is precisely balanced by the amount of infrared radiation emitted by the planet back to space. Now, in the case of a greenhouse effect, the visible light comes in just as it would have if there were no atmosphere, but the atmospheric gases invisible in the visible -- that is, transparent in the visible part of the spectrum -- tend to be opaque in the infrared part of the spectrum. The thermal radiation in the infrared is impeded from getting out. You can consider it a kind of blanketing of the Earth in the infrared and not in the visible part of the spectrum. As a result, the surface temperature has to go up unitl the radiation which is leaking out in the infrared where there isn't a lot of opacity just balances the visible radiation that is coming in. And such greenhouse effects can be very significant. In the Earth's atmosphere, the greenhouse effect is due mainly to carbon dioxide and to water vapor, with other constituents playing more minor roles, although oxides of nitrogen and other materials could be significant on a smaller scale. Now, the scientific community is in very good mutual agreement on the overall general consequences of the burning of fossil fuels, putting more carbon dioxide into the atmosphere of the Earth, producing an incremental greenhouse effect that is adding to the existing greenhouse effect. The greenhouse effect, I stress again, is a good thing. We owe our lives to it. And while differences between calculations have been stressed in the press, what is important is that all the calculations agree to the first order that doubling of the carbon dioxide in the Earth's atmosphere will increase the global temperature by a few degrees Centrigrade, something of that order. To require that scientists provide an absolutely ironclad, guaranteed value of how much the temperature will go up is probably asking too much. The calculations involve many factors, and you cannot be absolutely sure that you have included every one of them. What is striking is the unanimity of all of the calculations, so if a few degree increment in the global temperature is a bad thing then you ought to start worrying about what to do in that case. Also, you ought to start worrying about whether there is some way to avoid putting more carbon dioxide into the atmosphere. |
So, as I write this in 2013, we've known full well for over 30 years what is likely to happen. Scientists make predictions, and then we see if they come true. Sagan laid out the scientific position 30 years ago, and we see it coming true as they've foreseen.
Sagan was undoubtedly aware of the report issued by the National Academy of Sciences in 1979, the year of my high school graduation, which concluded that "For more than a century, we have been aware that changes in the composition of the atmosphere could affect its ability to trap the sun's energy for our benefit. We now have incontrovertible evidence that the atmosphere is indeed changing and that we ourselves contribute to that change. Atmospheric concentrations of carbon dioxide are steadily increasing, and these changes are linked with man's use of fossil fuels and exploitation of the land. Since carbon dioxide plays a significant role in the heat budget of the atmosphere, it is reasonable to suppose that continued increases would affect climate....
"The conclusions of this brief but intense investigation may be comforting to scientists but disturbing to policymakers. If carbon dioxide continues to increase, the study group finds no reason to doubt that climate changes will result and no reason to believe that these changes will be negligible. The conclusions of prior studies have been generally reaffirmed. However, the study group points out that the ocean, the great and ponderous flywheel of the global climate system, may be expected to slow the course of observable climatic change. A wait-and-see policy may mean waiting until it is too late." (from The National Academies Press publication Carbon Dioxide and Climate: A Scientific Assessment (1979)). An even earlier publication of the National Academies Press raised the same issue: the 1977 publication Energy and Climate: Studies in Geophysics. "The principal conclusion of this study is that the primary limiting factor on energy production from fossil fuels over the next few centuries may turn out to be the climatic effects of the release of carbon dioxide."
Another interesting quote occurs in the foreward: "One final thought. This report has been addressed to what might be the climatic impact over the next century or two of a major dependence on fossil fuels. In the light of a rapidly expanding knowledge and interest in natural climatic change, perhaps the question that should be addressed soon is, 'What should the atmospheric carbon dioxide content be over the next century or two to achieve an optimum global climate?' Sooner or later, we are likely to be confronted by that issue."
Author and climate change activist Bill McKibben took this quote to heart in the 21st century when he asked NASA scientist James Hansen for his opinion, and was told 350 parts per million. McKibben took that number and created the pivotal organization 350.org. Hansen has, however, since dropped his estimate to around 300 (or back to approximately pre-industrial levels). [No sign that McKibben will change the name of his group, but he may be grinding his teeth!]
Upshot: scientists, the best and brightest that our nation has to offer, have found "no reason to doubt that climate changes will result", and "no reason to believe that these changes will be negligible." [It's curious that they used the negative on that second statement, isn't it? "We doubt they'll be small changes," they might have said....]
It will be recorded that one of the hugest historical failings of all time is that short-sighted economic interests have taken it upon themselves to cloud the science, and seed the popular imagination with doubt about climate change when it was most important to take rapid action to avert it. How else will these obfuscators make their buck in carbon? In spite of the very solid theoretical background for climate change in the face of human activity, we find ourselves battling for the hearts, minds, and attention of the public.
It is maddening that, in spite of the scientific evidence, we still find articles like this one, published in a well-known U.S. magazine (Forbes) in 2013: "The New York Times' Global Warming Hysteria Ignores 17 Years Of Flat Global Temperatures". My favorite quote, if one can really call it a "favorite", is this one: "So where does the evidence needed to support the IPCC's 95 percent certainty [of anthropogenic climate change] claim come from? The true answer is that there simply isn't any. None at all. There never was...only totally unproven theoretical climate models." No data?
Ironic comment, especially given that essentially every major global scientific organization agrees that there is anthropogenic climate change, with at least 95 percent certainty. For example, in 2009 a letter went out to the United States Senate, alerting this august body of our elected representatives that "Observations throughout the world make it clear that climate change is occurring, and rigorous scientific research demonstrates that the greenhouse gases emitted by human activities are the primary driver. These conclusions are based on multiple independent lines of evidence, and contrary assertions are inconsistent with an objective assessment of the vast body of peer-reviewed science." (my emphasis)
That's the nicest way one could say that "deniers are liars."
The sender of this letter? A list of scientific organizations comprised of the following: the American Association for the Advancement of Science, American Chemical Society, American Geophysical Union, American Institute of Biological Sciences, American Meteorological Society, American Society of Agronomy, American Society of Plant Biologists, American Statistical Association, Association of Ecosystem Research Centers, Botanical Society of America, Crop Science Society of America, Ecological Society of America, Natural Science Collections Alliance, Organization of Biological Field Stations, Society for Industrial and Applied Mathematics, Society of Systematic Biologists, Soil Science Society of America, and the University Corporation for Atmospheric Research. Included among those organizations is the most influential association of applied mathematics in the world (the Society for Industrial and Applied Mathematics, or SIAM).
Now I would ask Mr. Larry Bell, who wrote the piece for Forbes, where did all these scientists and scientific organizations go wrong? And what does he know that they don't? [According to the Forbes website, he is a professor of Space Architecture at the University of Houston.] One wonders how Mr. Bell could justify the changes in plant hardiness that the USDA published in its maps (and which the EPA spotlighted in this publication):
