Global warming: American Meteorological Society says there’s no room for doubt on climate change

‘Prudence dictates extreme care’

Global July temperatures were the fourth-warmest on record. Graphic courtesy NASA.

By Summit Voice

SUMMIT COUNTY — While there are still a few prominent TV weather announcers who publicly question the overwhelming body of global warming science, the American Meteorological Society has updated its official position on climate change, acknowledging unequivocally “that Earth’s lower atmosphere, ocean, and land surface are warming; sea level is rising; and snow cover, mountain glaciers, and Arctic sea ice are shrinking. The dominant cause of the warming since the 1950s is human activities.”

“This statement is the result of hundreds of hours of work by many AMS members over the past year,” said AMS executive director Keith Seitter. “It was a careful and thorough process with many stages of review, and one that included the opportunity for input from any AMS member before the draft was finalized,” Seitter said. The full statement is online at the AMS website.

After describing in detail what’s known about climate change, the AMS statement ends with a poignant warning: “Prudence dictates extreme care in accounting for our relationship with the only planet known to be capable of sustaining human life.”

The organization recently took some flak from environmental activists who want weather forecasters to discuss how climate change might be affecting what people experience in their day-to-day weather. One group, Forecast the Facts, publicly called out TV weather forecasts by name. The group also published a study suggesting that 27 percent of TV weather forecasters call global warming a scam, while half deny that global warming is caused by emission of greenhouse gases. Grist.org covered this topic here.

It’s not clear if the revised statement will change the way forecasters present their weather info, but for other purposes, the new document provides a clear and elegant outline of climate change, including impacts to the polar regions, where “Arctic sea ice extent and volume have been decreasing for the past several decades.” The statement explains that both the Greenland and Antarctic ice sheets have lost significant amounts of ice and that most of the world’s glaciers are in retreat.

The AMS also touched on the hotly debated subject of links between climate change and extreme weather, referencing studies showing that the amount of rain falling in very heavy precipitation events (the heaviest 1 percent of all precipitation events) has increased over the last 50 years throughout the U.S.

Other climate-change impacts are also discussed directly:

“Freezing levels are rising in elevation, with rain occurring more frequently instead of snow at mid-elevations of western mountains. Spring maximum snowpack is decreasing, snowmelt occurs earlier, and the spring runoff that supplies over two-thirds of western U.S. streamflow is reduced. Evidence for warming is also observed in seasonal changes across many areas, including earlier springs, longer frost-free periods, longer growing seasons, and shifts in natural habitats and in migratory patterns of birds and insects.”

There no dithering about sea level, which according to the best available measurements has risen by about 7 inches in the 20th century, with the rise accelerating since the early 1990s.

The statement also makes it clear that the observed changes are “beyond  what can be explained by the natural variability of the climate.” Extensive scientific evidence makes it clear that  “the dominant cause of the rapid change in climate of the past half century is human-induced increases in the amount of atmospheric greenhouse gases, including carbon dioxide (CO2), chlorofluorocarbons, methane, and nitrous oxide”

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12 Responses

  1. “beyond what can be explained by the natural variability of the climate.”

    That is what I really want to understand: How does anyone know that?

    • The answer is simple enough. We have more than 100 years of direct observations, and we can deduce past climate by various means — tree rings, atmosphere trapped in old ice, pollen in sediments, etc. We know how much and how fast climate has varied in the past. The climate currently is changing very fast, weather events such as deluges and droughts that used to be extremely rare or have never happened in recorded history are becoming commonplace, glaciers and sea ice that have existed for tens of thousands of years are disappearing, and high temperature records are exceeding low temperature records by — recently — almost 20 to 1.

      So yes, we know that.

      • Pretty thorough answer Cervantes. But from what I’ve seen, no answer is thorough enough to convince someone who is determined to deny, for political or emotional reasons, that humans affect the world around us.

        It’s like trying to convince the Pope to become an atheist.

    • The climate system is noisy: temperatures, precipitation, have long and short term variations, making it difficult to discern a real effect from the noise.

      After 30 years, it has not been found that the changes that we are seeing today are beyond the limits of the natural noise, which indicates an artificial cause: carbon dioxide pollution.

      We are adding about 130X the amount of CO2 into the atmosphere per year today, than volcanoes do. The result is the climate change that we are seeing today.

    • The phrase ”natural variability” makes it all sound a little random. We actually understand fairly well the forces at work that make climate vary from year to year, decade to decade, century to century, milennium to milennium, etc. We understand orbital cyclings, solar cyclings, regional oscillations (AO, NAO, ENSO, etc.), global circulation patterns, changes in albedo, changes in greenhouse gases, changes in aerosols (like SO4) and many minor feedbacks. One of the few feedbacks we don’t understand as well as we’d like is clouds. Cloud studies like Dessler (2010), though, indicate that whether or not the cloud feedback is net positive or negative, it’s not likely significant. All of these forcings and feedbacks are taken into account when determining climate sensitivity and when analyzing things like surface temp.

      For example, if you look at the global surface temp record for the past 30 years, it looks pretty jagged. There are lots of ups and downs, but the temp generally rises. It appears to flatten out after 1998–at least for about a decade. Now, we could say that ”temp is not rising, therefore there is no global warming.” That, however, would not take into account the effect of known variables. If we strip out the signals of a set of variables and leave selected ones alone, then we can see the effect of those left alone. Foster & Rahmstorf (2011) is one such study. It takes an ensemble of five surface temp/lower troposphere analyses (RSS, UAH, GISS, Had3, and BEST) and strips out the signals from solar, aerosols, and La Nina/El Nino, all for the past 30 years. The jagged line then becomes much smoother, and the trend is clear: about .17C per decade for the past three decades. That signal–what’s left–is largely the signal from greenhouse gases. There are no other forcings/feedbacks that could create such a powerful signal, and the signal is consistent with the basic physical theory of greenhouse gases. The actual study was published in the well-respected Environmental Research Letters, and it has a paywall. Foster talks about the study on his blog: http://tamino.wordpress.com/2011/12/06/the-real-global-warming-signal

      Climate modelling, upon which the basic theory of AGW is >not< based, takes all of this into account when running projections. The IPCC model runs for AR4 (2007) do well at projecting things like surface temp increase and changes in drought, precipitation, and heat extremes. They don't do as well with complex sub-systems like sea level rise (IPCC AR4 underestimated sea level rise) and Arctic sea ice decline (IPCC AR4 severely underestimated Arctic sea ice decline). AR5, next year, will likely have a much more sophisticated modeling base.

    • Warming has been going on since the end of the ice age. Models generated to fit psuedo-thermetric data generated using homoginized temperature data with a bias to higher temperatures do not fit the data for the last 10 years. About 2000 we reached the point Krakatau cooling effects should have been exceeded so we should have more record temperatures unless we get a mother nature event. American geophysical union shows gobal CO2 and Methane levels could plateau in 50 years by abandoning coal power generation and using shale gas. When the noise level is so high in measurement methods that you can not discriminate with any statistical significance, we are going to somehow conclude a magical year of 1950 for a starting point (maybe it was atmospheric bomb testing?). A 27% disagreement of experts is not one loose cannon but an indication something stinks. Lets get rid of coal in america, put in dual cycle power plants, take care of America’s contribution to warming and head down the road with a modern reindustrialization. There are too many Fu@@#@# liars in this game. Take care of the country. REMEMBER, oil used to sit on top of the ground in pools before drilling became required to find more!! Shale gas is the global effort without bankrupting our economy. Get it right based on DATA and get the politics OUT!!!

  2. It is a greater and steeper rise in both CO2 atmospheric content and temperature than any in the records. Look up the famous 100,000-year cycle plots of Vostok ice core data; look at the 800,000-year graph. Past data is there in abundance, from a large variety of sources (this graph uses one source, bubbles in ice going back nearly 1 million years).

  3. Global warming is do to changes in earth orbit and tilt, cycles of warming are based on the proven Malenkovich effect.

    Look it up you will find a logical explaination, this planet will continue to warm for the next perhaps 10,000 years, then glaciers will return in time to New York City and humans will be devastated in population, like all previous cycles, that is reality.

    • Actually, this is my field; it’s not something I just read about on the Internet or took a few courses on. A plethora of data out there if you’re truly interested in reality. Certainly start with orbital cycles and such. The 100,000-year, 40,000-year, and roughly 22,000-year cycles are part of the groundwork, as it were, along with many other factors. And yes, it’s quite frightening that a cycle that has been roughly repeating itself for at least a million years can be changed out of all recognition so quickly. Will we ever go into another glacial? That’s a big question. There’s pretty good evidence that climate was already bumped out of its “natural” slide back into glacial times between 5,000 and 8,000 years ago, by humans. You might want to read up on carbon and oxygen isotopes (stable isotopes). That may help clear things up a bit.

      • Certainly not frightened by the near term prospect of warming and certainly not familiar with the distribution of or findings of carbon, chromium or iridium isotopes. Would not argue with you on the topic, however, find it impossible for humans population 8,000 years ago to dramatically impact any of the globe. Recent DNA findings indicate that only 40 to 60 people crossed the frozen Bering Sea to populate North and South America. Can buy an argument that weather in the last 75 years has been changed by human population, but only due to lack of other natural geophysical occurences.

        We as a species have been lucky to be on this planet during a time of global warming and a time without notable volcanism or other challenges to our existence, ie, iron core meteorites. Our recent human history has seen numerous occasions of significant cooling, such as during the Revolutionary War, and further back in recorded history in the mid 1400′s. When the planet warmed, their was no call to tax those that survived.

        My view on the subject is based more on politics and is ……do not tax me for living on this globe, because a politician or the government cannnot keep itself in financial order and are unable and for sure incapable of solving the impact of natural causes, anyway.

  4. It must be understood that even while Shell is asking for more time to explore drilling in the arctic sea (well prepared to move into that territory knowing that the ice would be melting) the petroleum/carbon companies are still spending millions to pr agencies for hiring people to do commentary posting encouraging denialism.

    Denialism Sockpuppets.

    Why? For the exact same reason the tobacco companies hired PR companies to promote denialism of the cancer/smoking connection.

    Litigation.

    They know that at this point they are and will be liable for the wrecking of world economies, agricultural disasters and deaths.

    One of these days they will have to face the music in a court of law. But they are trying to put that off using the court of stupidity – relying on ignorant people to support them – for as long as possible.

    I wonder how long those ignorant people will be willing to do so- looking at the massive energy bills they must be paying this summer in the heat zones of the US.

  5. [...] 2012/08/28: SummitCV: Global warming: American Meteorological Society says there’s no room for… [...]

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