Global Warming -- the facts

Global Warming – the facts


Much ink has been spilled, breath expended and heat generated over the subject of global warming, often in the form of uninformed and often partisan opinion and unjustified accusatory diatribes. In an attempt to clear the air, I would like to present what is known about current climate change and how well we know it. I will make no predictions, references to societal impact or include any political opinions; instead I will present only the science and how well we know it. Readers can draw their own conclusions about the future.

I will base this essay partly on the Synthesis Report derived from the 2007 Intergovernmental Panel on Climate Change (IPCC), which was prepared by approximately 50 scientists from a much larger document derived from the research of many more climate scientists, including those from Penn State. Although public discussion seldom includes known uncertainties in the data, I will attempt to provide some balance by referring to the IPCC confidence levels (in italics).

Global average temperatures, based on almost 30,000 data series , show small fluctuations from year to year amidst a clear rise of almost 1 degree Fahrenheit (° F) between 1910 and 1940. Global average temperature remained fairly flat from 1940 to 1960, after which it rose once again with increasing steepness by another degree until the ‘present’ (2007). Eleven of the previous twelve years (1995-2006) rank among the warmest years of the instrumental record since 1850. Increases are widespread over the entire globe, are greater at northern latitudes and tend to be smaller in the southern hemisphere than the northern hemisphere.  Antarctica may be experiencing little change. Changes in the arctic regions are almost double the global rate. Average temperatures have also increased in the oceans down to at least 3000 feet. New analyses of balloon sounding data show warming rates over the mid and lower troposphere to be similar to those observed at the surface.

The IPCC document expresses a very high degree of confidence in these observations, adding that it is very likely that cold days, cold nights and frosts have become less frequent, and likely that heat waves have become more frequent over most land areas.  Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50 – year period in the last 500 years and likely highest in the past 1300 years.  The IPCC report acknowledges medium confidence that the warming has resulted in earlier spring planting of crops and longer growing seasons, but also increased heat related mortality and changes infectious disease rates in Europe.

Sea level has been rising from the year 1870 when it was first measured -- first gradually by about an inch up to about 1930 and thereafter more rapidly by another 5- 6 inches by 2007. Over half of this rise is attributable to the thermal expansion of the oceans (due to the temperature increase) with the remainder due to loss of sea ice and polar ice sheets. Impacts on coastal wetlands and mangroves, including coastal flooding and damage are suspect but not yet established trends.  It is likely, however, that the frequency of extreme high sea levels increased in many locations.

Northern Hemisphere snow cover remained constant from 1920 until 1980 but thereafter experienced a significant decline of several million square kilometers.  A high degree of confidence is placed on observations showing the enlargement and increasing size of glacial lakes, increased glacial runoff and earlier spring peak discharge in many glacier- and snow-fed rivers

There is high degree of confidence that the warming is affecting terrestrial biological systems and also freshwater biological systems, as well as related changes in ocean salinity, oxygen levels and circulation. Impact of global changes on coral reefs is becoming increasingly evident, though the exact causes remain unclear.

The question is whether human activity is causing these changes. The 30% increase since 1890 in the primary greenhouse gas, carbon dioxide (an irrefutable statistic), is the largest increase in almost a million years. The most convincing evidence that this increase is due to human activity is that the rise is roughly equivalent to the amount of carbon consumed by the burning fossil fuels during that time.

Nearly a decade ago calculations by climate scientists finally produced highly convincing evidence of the effects of human activity on global climate change. Unlike previous types of computer simulations, these simulations included the novel approach of simulating the present  (year 2000) global temperature starting in the past with the year 1890. Two series of four computer simulations were made under the auspices of the National Center for Atmospheric Research (NCAR) and the Department of Energy using several different climate models, called General Circulation Models (GCMs). One series of computer runs included only the effect of volcanic eruptions and solar variations on the earth’s radiation budget. Aerosol particles such as sulfates and the notorious greenhouse gas, carbon dioxide, were kept constant at their 1890 levels. Another series of simulations allowed the sulfates, aerosols and greenhouse gases to vary according to their observed values. Simulations allowing greenhouse gasses to change as measured showed almost exact agreement with measured global temperatures, whereas those simulations in which greenhouse gasses were kept constant were unable to simulate the observed warming after 1960. These simulations were decisive in my thinking about global warming.






"high degree of confidence"

Here's something that is fascinating - even tho I understand and tend to strongly agree with all the arguments and statements that you've made in this piece, I feel pretty certain that it would read as gobbledegook to the average layperson.

Take the phrase "high degree of confidence", which you use several times and italicize to show it's provenance. I agree with your assessment - but I think the layman would parse that phrase differently. I think they would interpret it as meaning "this is what we want you to believe".

The layman is not used to the type of thinking and assessment that uses a statistical claim like "high degree of confidence". It's not part of the conversations and rhetoric they encounter in their normal routines, so it's got to be regarded with suspicion.

I've debated right wingers and warming deniers in some depth and with some intensity here and there on the net, so I have a pretty good practical idea of what type of rhetoric they use and how they will react to statements like high degree of confidence.

And you probably already know that the IPCC is a favorite target of the deniers, so for them, simply invoking their reports automatically disproves anything you argue based on them.

This is part of what makes global warming so politically contentious.

I see this as one of the major problems affecting human societies around the planet these next few centuries. Our popular culture isn't giving us the mental tools to be able to understand what science culture is saying, or to really understand how and why the claim of high degree of confidence is being made, and what it means.

This is a realy important problem. How do we make science culture more transparent and easy to understand by the laymen?

And how does science culture behave in the political areana, into which it will increasingly be drawn?

I thought this was the big lesson of the East Anglia emails. The stress between the demands of science culture and the demands of political culture.

response to Bill's comments

Bill, I have a high degree of confidence in your ability as an editor
for Voices. Is that an ambiguous statement? In any case, the wordage
is exactly that of the IPCC repor; I didn't want to change or start to
interpret what the document says. The material I presented is data,
not interpretation, not a prediction. The degree of confidence
probably refers to the variance and thus the statistical confidence
limits, in the data, but those terms, I agree, would have been
bewildering to the public. The average of 30,000 records is what it
is. Someone can dispute the average, but unless they are willing to go
back over the records and compose their own average, they are simply
voicing an untutored opinion based on ignorance or wishful thinking.
The number is not a matter of opinion. My guess is that whomever has
criticized the IPCC report has (1) never read it; (2) never read the
scientific papers behind it; (3) doesn't understand the physics or the
models that relate CO2 to temperature.

Anyway thanks for your feedback. You were apparently the only one to
provide feedback to me for my previous and, I had thought, provocative
essay. Maybe we are all just preaching to the choir.

BTW, I find the American public amazingly ignorant of science (among
other things). Amazing because the average yahoo will submit to the
latest technology at his or her dentist or doctor, flash his ipad,
gps, or feel gleeful over the latest military weapon without realizing
that he is trusting modern science to provide these things. They
automatically assume that we are like politicians, ready to lie in
order to gain advantage. We can't fight back because we do not have
the luxury of deception or deviousness at our disposal. In the end,
truth always wins, however.


Dude, I know EXACTLY what "high degree of confidence" means, I'm a science geek. I'm however in the top percentiles of general science and science culture knowledge, and CAN'T be your target audience, so I picked something that I know the average denier would lampoon, and used it to center my commentary.

My goal was to talk about ways of making science culture more accessible - and as It happens, I believe that's something that science and scientists have to work on, because pop culture will NOT work on it.

Anyways, I really hope you will post what you just wrote to me as a reply to me on your blog post. This is an important conversation imnsho.


note: reprinted with permission from an email exchange

Could be good if the republicans investigate global warming ...

I read a page in the LA times that said that one of the things the republican leadership say they will do now is investogate global warming scientists and the EPA, etc etc. It was from just before the election.,0,6040861.story

The GOP's fire will be concentrated especially on the administration's efforts to use the Environmental Protection Agency's authority over air pollution to tighten emissions controls on coal, oil and other carbon fuels that scientists say contribute to global warming.

The attack, according to senior Republicans, will seek to portray the EPA as abusing its authority and damaging the economy with needless government regulations.

In addition, GOP leaders say, they will focus on what they see as distortions of scientific evidence regarding climate change and on Obama administration efforts to achieve by executive rule-making what it failed to win from Congress.

Even if Republicans should win majorities in both the House and Senate, they would face difficulties putting their views into legislative form, since Senate Democrats could use the threat of filibuster to block bills just as the GOP did on climate and other issues during the past year.

This could be an interesting turn of events - altho I figure the republican leadership is smart enough to avoid anything at all that actually examines the science, they could certainly appeal to their base in a relatively low cost way by attacking the EPA.

But, if we are lucky, we might require the republicans to investigate the science itself, or maybe they will so accomodating as to have investigations of "climategate".

I posted here somewhere a pdf and quotes from one or several of the investigation reports of the stolen East Anglia emails - but those reports are not well known, it would be educational to have them brought back into public attention by a congressional inquiry.

And congressional investigations could be a force that engendered a bit more scientific literacy in folks that don't have much of a need or taste for the stuff.

bill's comments

The Democrates still controls the senate. I wonder what the public will think, especially if the economy does not improve, of a party that will spend all its energy trying to reverse what the other party has done. The public is fairly divided on global warming and, I suspect, mildly in favor of the health care plan. Trying to take health care away from 40 million people while allowing the air and water to become less healthy should not play very well. Moreover, the next election, a presidential one, is typically more propitious for the party in power in the White House. It will be an interesting couple of years.



The republicans have no actual policy, so smokescreens will be..

The republicans have no actual policy, so smokescreens and phoney media activity (in lieu of legislation and jobs) will be the order of the day I expect. Anything they can do to distract the public while they let the corporations continue to move real wealth out of the country, they will do.

I am hoping they carry out their threats to investigate global warming science, as clearly they plan to do, google news is filled with articles about it now.

Science culture has been too insular, and needs to change. By it's very nature it needs some insularity, it's methodology requires specialization, and the way our society funds and manages scientific research creates a specialized culture of financially dependent and highly, even cruelly competitive individuals.

But, hard times are coming, as a perfect storm of resource depletion, global warming, and population pressures turns scientists from isolated "monks" into the only chance our society has to survive.

We just haven't realized this yet as a society and a civilization - we are in the last decade or two of the cheap oil age, still living off our capital and off of borrowed money and the priviledges of empire - so we think we can use science and scientists as political pawns to protect the fossil carbon industry.

Science culture needs this shock, so that it develops new tools to communicate with non-scientists and the corporate media.

It's going to suck tho, as it unfolds. At first the republicans WILL be able to terrorize the science community and impose fossil-carbon industry propaganda into the media, just as the tobacco industry did for so many decades.

Politics is fast, global warming is slow, so politics will appear to win. We have to get used to it.



bill's comment about global warming

Thanks for taking the time out to respond to my essay. Sometimes I think that you are the only person who reads them. In any case, I very much agree with your comment about hard times to come and the role of science. I think that scientists should no longer play a passive role but to speak out and to speak out aggressively, whether in print or when called before Congress, to accuse the deniers of McCarthyism and the equivalent of the Nazi book burning. Tell them that they can ignore or intimidate scientists but they will have to live with the truth, which doesn't depend on ignorance or any amount of intimidation.

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