The Smoking Gun

global warming chart

FIGURE SPM-5. Projected surface temperature changes for the early and late 21st century relative to the period 1980–1999. The central and right panels show the Atmosphere-Ocean General Circulation multi-Model average projections for the B1 (top), A1B (middle) and A2 (bottom) SRES scenarios averaged over decades 2020–2029 (center) and 2090–2099 (right). The left panel shows corresponding uncertainties as the relative probabilities of estimated global average warming from several different AOGCM and EMICs studies for the same periods. Some studies present results only for a subset of the SRES scenarios, or for various model versions. Therefore the difference in the number of curves, shown in the left-hand panels, is
due only to differences in the availability of results.

Its here, one of the most comprehensive studies ever done on global warming. With over 2500 scientists, over 800 contributing writers, 450 lead authors from over 130 countries, taking over 6 years to produce this one amazing report. The Intergovernmental Panel on Climate Change (IPCC) has done a wonderful job of bringing so much mental power to bear on studing this problem.

In essence this is a “read it and weep” moment for anyone who accepts science but not human caused global warming, for thouse who refuse to accept science this wont do anything for you.

This is a sober and strongly worded message to the world, do something, and do it now. Its far too late to stop the harmful effects of what we have already done, but its not too late to prevent even worse things from happening. Global warming is going to hurt us, badly, but if we act soon it wont kill us. You know what they say about things that don’t kill you…

From the study summary:
Download the summary and read it for yourself here (pdf)

Global atmospheric concentrations of carbon dioxide, methane and nitrous oxide have increased markedly as a result of human activities since 1750 and now far exceed pre-industrial values determined from ice cores spanning many thousands of years. The global
increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change, while those of methane and nitrous oxide are primarily due to agriculture.

Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice, and rising global mean sea level

melting ice

From other sources:

The Intergovernmental Panel on Climate Change (IPCC) said temperatures were probably going to increase by 1.8-4C (3.2-7.2F) by the end of the century.

It also projected that sea levels were most likely to rise by 28-43cm, and global warming was likely to influence the intensity of tropical storms.

The findings are the first of four IPCC reports to be published this year.

“We can be very confident that the net effect of human activity since 1750 has been one of warming,” co-lead author Dr Susan Soloman told delegates in Paris. BBC

global warming chart

he world’s leading climate scientists, in their most powerful language ever used on the issue, said global warming is “very likely” man-made, according to a new report obtained Friday by The Associated Press.

The report provides what may be cold comfort in slightly reduced projections on rising temperatures and sea levels by the year 2100. But it is tempered by a flat pronouncement that global warming is essentially a runaway train that cannot be stopped for centuries.

“The observed widespread warming of the atmosphere and ocean, together with ice-mass loss, support the conclusion that it is extremely unlikely that global climate change of the past 50 years can be explained without external forcing, and very likely that is not due to known natural causes alone,” said the 20-page report.

Human-caused warming and rises in sea-level “would continue for centuries” because the process has already started, “even if greenhouse gas concentrations were to be stabilized,” said the 20-page report from the Intergovernmental Panel on Climate Change.

The phrase “very likely” translates to a more than 90 percent certainty that global warming is caused by man.

What that means in layman’s language is “we have this nailed,” said top U.S. climate scientist Jerry Mahlman, who originated the percentage system. CNN(bolding mine)

If carbon dioxide concentrations in the atmosphere reach twice their pre-industrial levels, the report said, the global climate will probably warm by 3.5 to 8 degrees. But there would be more than a 1-in-10 chance of much greater warming, a situation many earth scientists say poses an unacceptable risk.

Many energy and environment experts see such a doubling as a foregone conclusion sometime after midcentury unless there is a prompt and sustained shift away from the 20th-century pattern of unfettered burning of coal and oil, the main sources of carbon dioxide, and an aggressive quest for expanded and improved nonpolluting energy options. NYtimes

Global warming “is now evident” from several sources. Ocean warming now extends to a depth of at least 3,000 metres (9,750 feet) as the seas take up heat from the air. Mountain glaciers and snow cover have declined in both hemispheres. Sea levels rose globally by 1.8 millimetres (0.07 inches) per year from 1961 to 2003 but this pace accelerated to 3.1 mm (0.12 inch) per year from 1993 to 2003.

Most of the rise was due to thermal expansion because water expands when it warms. The rest was due to runoff from glacier and snow met.

— Since the 1970s droughts have been “more intense and longer” and observed over wider areas, especially in the tropics and subtropics.

— From 1900 to 2005, rainfall increased “significantly” in eastern parts of North and South America, northern Europe and northern and central Asia, while drying occurred in the Sahel, Mediterranean, southern Africa and parts of southern Asia.

— The top layers of the Arctic permafrost have warmed by up to 3.0 degrees C (5.4 degrees F) since the 1980s. The maximum area of seasonally frozen ground has decreased by around seven percent in the northern hemisphere since 1900.

FORECAST FOR 21ST CENTURY:

— By 2100, global average surface temperatures could rise by between 1.1 C (1.98 F) and 6.4 C (11.52 F) compared to 1980-99 levels. These figures come from computer simulations based on how much carbon dioxide (CO2), the principal greenhouse gas, is in the air.

The lower figure is the “B1 scenario”, which is based on a fast-track switch to cleaner energy and sustainable development. The higher figure is the “A1F1 scenario”, in which fossil fuels are still burned intensively. — Inside this broad temperature range, the most likely surface temperature rise will be between 1.8 and 4.0 degrees C (3.24 and 7.2 degrees F). In 2001, the IPCC predicted a range of between 1.4 and 5.8 degree C (2.52 and 10.4 degrees F).

— Sea levels will rise by between 18 and 58 centimetres (7.2 and 23.2 inches), again based on how much CO2 is in the air. In the 2001 report, the estimate was 9.0 to 88 cms (3.5 to 35 inches). The IPCC says the revision is because of improved estimates as to how the oceans absorb heat. — Warming will occur most over land at high northern latitudes and least over the Southern Ocean and the North Atlantic.

— Higher CO2 levels will lead to increasing acidification of the oceans, whose micro-organisms absorb carbon dioxide at the surface.

— Snow cover will contract further and the depth of thaw in most permafrost reasons will increase. Sea ice is projected to shrink in both the Arctic and Antarctic under all CO2 models. In some projections, the Arctic will be virtually free of late summer sea ice by the latter part of the 21st century.

— Hot extremes, heatwaves and heavy precipitation events are “very likely” to become more frequent.

— Typhoons and hurricanes are likely to become more powerful, packing higher wind speeds and more intense rainstorms but the evidence about whether they may decrease in number is inconclusive. Extra-tropical storms will track poleward.

— The Gulf Stream is “very likely” to slow down. Projections suggest an average slowdown of some 25 percent during the 21st century. But this should not plunge western Europe into a new Ice Age. Higher air temperatures will help compensate for the loss of warmth from this balmy Atlantic current.

— Antarctica: There is no evidence at the moment that the Antarctic icesheet will suffer widespread melting this century as it is such a huge, cold mass. Some studies project it will gain in mass due to increased snowfall. But others suggest a net loss of mass if coastal glaciers start to run more swiftly.

BEYOND THE 21ST CENTURY:

— Carbon emissions this century “will contribute to warming and sea-level rise for more than a millennium”, due to the timescale required for greenhouse gases to degrade.

— The Greenland icesheet will continue to contract beyond 2100 and contribute to the global sea level rise. Models suggest a rise of 1.9 to 4.6 degrees C (3.42 to 8.3 degrees F) in global average temperatures compared to pre-industrial times would, if sustained for millennia, virtually eliminate the Greenland icesheet and drive up sea levels by seven metres (22.75 feet).

AREAS OF CERTAINTY AND UNCERTAINTY:

— The IPCC says it has greater confidence in the accuracy of its short-term projections. It had predicted warming of between 0.15 and 0.3 degrees C (0.27 and 0.54 degrees F) per decade for 1990-2005. The warming turned out to be 0.2 degrees C (0.36 degree F), right in the middle of the range.

— It also says it can forecast with greater confidence rises in temperature, rainfall, extreme weather events and ice response at regional level.

— Positive feedbacks: These are events that could swiftly increase global warming by dumping into the atmosphere greenhouse gases that have been stored, for instance, in the soil or by slowing or stopping processes that absorb CO2 from the air. Positive feedbacks are poorly understood. “The magnitude … is uncertain” and this makes it hard to accurately project scenarios at which CO2 will stabilise, which is a key factor in policy making.WBCSD

So basically we have the vast vast vast majority of the words top climate scientists telling us that global warming is real, its caused by humans, and we better damn well do something about it(with a 90% certainty level). If I told you there was a 90% chance that you would be struck by a bullet unless you moved, would you duck?

4 thoughts on “The Smoking Gun”

  1. I was somewhat shocked and saddened today when I told a fairly smart and well-educated friend about the 2007 Assessment Report and the recent Summary. He replied to me:

    “I will never believe that hamstringing our economy to reduce CO production will make any meaningful difference. The human effect on climate is mostly consensus based, not scientifically based. Probably never will be…”

    I almost couldn’t believe what I was reading, or at least that this friend of mine had written it.

    It really takes a lot of patience to help folks open their eyes.

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