Amounts of warming previously thought to be safe may instead trigger widespread melting of the world’s ice sheets and other catastrophic impacts, scientists said….

“There’s evidence that climate sensitivity may be quite a bit higher than what the models are suggesting,” said Ken Caldeira, a senior scientist at Stanford University’s Carnegie Institution for Science.

That’s from a Daily Climate piece on this panel discussion at last weeks AGU meeting:

The sensitivity issue is a complicated one, as I’ve discussed.  The AGU discussion certainly helps clarify key issues and suggests that some effort is being put into a reconciliation of the different ways of  calculating.

Don’t miss the back and forth on whether we are headed toward 25 meters of sea level rise or 70 meters at the end.  For some of the science, see Science: CO2 levels haven’t been this high for 15 million years, when it was 5° to 10°F warmer and seas were 75 to 120 feet higher — “We have shown that this dramatic rise in sea level is associated with an increase in CO2 levels of about 100 ppm”.

If you’re interested on Caldeira’s work on a very high sensitivity –  5.5°C to 8°C (10 to 14 F) — click here.  It is based on the PETM 55 million years ago and “having strong functioning methane feedbacks.” Thankfully we’ve got nothing to worry about in the Anthropocene (see”NSIDC : Thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100).

Here’s more of the Daily Climate piece:

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One of the world’s top climatologists talks climate science and climate science denial:

Related Posts:

• WashPost: “The Scientific Finding that Settles the Climate-Change Debate” and “Confirms” the Hockey Stick Graph
• Score Another Victory for Scientists, Michael Mann and the Freedom of Inquiry
• Much-vindicated Michael Mann and Hockey Stick get final exoneration

• Two more independent studies back the Hockey Stick: Recent global warming is unprecedented in magnitude and speed and cause

Over the past 10 years, the death of forest trees due to drought and increased temperatures has been documented on all continents except Antarctica. This can in turn drive global warming by reducing the amount of carbon dioxide removed from the atmosphere by trees and by releasing carbon locked up in their wood.

That’s from the news release for a new Proceedings of the National Academy of Sciences study, “Roles of hydraulic and carbon stress in a widespread climate-induced forest die-off.”

A common myth is that higher levels of CO2 will be good for all vegetation.  Unfortunately, those higher levels of CO2 are accompanied by higher temperatures and, in many places, drought and bark beetle infestation, which are bad news for trees — as study after study has documented (see links below).

The new study spells this out for the trembling aspen (Populus tremuloides), which goes by many other names, including the white poplar, though, as it turns out, the aspens apparently now have reason to tremble — manmade global warming.  Fittingly, the aspen die-off is “called Sudden Aspen Decline or SAD.”

The study has a nice overview and notes with the key recent studies:

Forests are important carbon sinks, yet they are threatened by global change (1, 2). In the past decade, widespread forest mortality related to drought or temperature stress has been documented in multiple biomes and on all vegetated continents (3–6). In temperate North America, some of these events have been linked to “global change-type droughts,” defined as severe drought coupled with elevated summer temperatures (6–9). Such mortality events can radically transform regional land cover and effect biodiversity, fire risk, ecosystem function, land–atmosphere interactions, and ecosystem services (10–12). Furthermore, forest diebacks can lead to dramatic decreases in net primary production and carbon sequestration, driving these ecosystems to become CO2 sources and to have a positive feedback to climate warming (11, 13–17). Climate-mediated die-off of pine forests caused by insect outbreak in Canada led to estimated carbon emissions of 990 Mt CO2e (CO2 equivalent) over a 20-y period, equivalent to 5 y of Canada’s annual transportation sector emissions (200 Mt CO2e/y) (15)

There is every reason to think things will get much worse if we stay on our current emissions path (see Science: Second ’100-year’ Amazon drought in 5 years caused huge CO2 emissions. If this pattern continues, the forest would become a warming source).

This PNAS study explores the cause of the climate-induced forest die-off, and explains how droughts kill trees:

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by Christine Shearer, in a Conducive Chronicle cross-post

In a recent article in National Journal, Americans for Prosperity (AFP) President Tim Phillips said there is no question that AFP and others like it have been instrumental in the rise of Republican candidates who question or deny climate science: “We’ve made great headway. What it means for candidates on the Republican side is, if you … buy into green energy or you play footsie on this issue, you do so at your political peril.”

AFP is a section 501(c)(4) organization, meaning it does not have to disclose its donors, but has been tied to significant funding from the Koch Family Foundations – founded by the billionaire Koch brothers of Koch Industries – as well as smaller donations from companies like ExxonMobil. Koch Industries and ExxonMobil are among the largest funders of studies questioning climate change science, often drawn upon by conservative politicians to legitimize their view that regulation of greenhouse gases (GHGs) is not needed because the science is still under debate.

These organizations and their supporters say they are just funding their own independent studies of climate change science. Yet these studies almost all go against observable scientific data to question global warming – so much so that one study funded in part by the Kochs that confirmed a rise in average world land temperature was regarded as an anomaly. Which raises the question: if these studies are largely designed not to shed light on climate change, but to create doubt and confusion to delay greenhouse gas regulations, why is it legal, and do those deliberately spreading misinformation face liability?

The first question, as far as I can tell, apparently boils down to: it’s legal because we have yet to make the deliberate manipulation of science illegal.

Yet while people and companies enjoy the First Amendment right to free speech, legal scholars have argued that right does not extend to influencing people under false pretenses. According to former tobacco industry lawyer Stephen Susman, when it comes to fossil fuel companies and supporters funding their own research on climate change, if “they knew the information they were spreading was false and being used to deliberately influence public opinion—that would override their First Amendment rights.”

This question may soon be playing out in the courts.

History of the science

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Back in 2009, NASA’s Gavin Schmidt was asked, “what percentage of global warming is due to human causes vs. natural causes?”  His answer:

Over the last 40 or so years, natural drivers would have caused cooling, and so the warming there has been … caused by a combination of human drivers and some degree of internal variability. I would judge the maximum amplitude of the internal variability to be roughly 0.1 deg C over that time period, and so given the warming of ~0.5 deg C, I’d say somewhere between 80% to 120% of the warming. Slightly larger range if you want a large range for the internal stuff.

Turns out he was spot on.

A new study in Nature Geoscience, “Anthropogenic and natural warming inferred from changes in Earth’s energy balance” (subs. req’d) finds:

Our results show that it is extremely likely that at least 74% of the observed warming since 1950 was caused by radiative forcings, and less than 26% by unforced internal variability. Of the forced signal during that particular period, 102% (90–116%) is due to anthropogenic and 1% (−10 to 13%) due to natural forcing….  The combination of those results with attribution studies based on optimal fingerprinting, with independent constraints on the magnitude of climate feedbacks, with process understanding, as well as palaeoclimate evidence leads to an even higher confidence about human influence dominating the observed temperature increase since pre-industrial times.

Here’s a figure from the study comparing the magnitude of different “forcing agents” or contributors to warming since the 1950s:

Contributions of different forcing agents to the total observed temperature change. Error bars denote the 5–95% uncertainty range. The grey shading shows the estimated 5–95% range for internal variability. Observations are shown as dashed lines.

The Nature News and Scientific American stories have had misleading headlines:

Three-Quarters of Climate Change Is Man-Made

That’s not a good headline.

The 74% or “three quarters” probability is where the 95% confidence level is for this one study.  As climatologist Kevin Trenberth put it in an email, it is “highly likely” that all of the warming since 1950 is due to human activity:

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Upwelling seawater along parts of Pine Island Glacier Ice Shelf has carved out caves in the ice. A new study links CO2 and Antarctica glaciation.

The news release for a new Science study, “The Role of Carbon Dioxide During the Onset of Antarctic Glaciation” (subs. req’d), explains:

A drop in carbon dioxide appears to be the driving force that led to the Antarctic ice sheet’s formation, according to a recent study led by scientists at Yale and Purdue universities of molecules from ancient algae found in deep-sea core samples.The key role of the greenhouse gas in one of the biggest climate events in Earth’s history supports carbon dioxide’s importance in past climate change and implicates it as a significant force in present and future climate….

“The evidence falls in line with what we would expect if carbon dioxide is the main dial that governs global climate; if we crank it up or down there are dramatic changes,” [co-author Matthew} Huber said. “We went from a warm world without ice to a cooler world with an ice sheet overnight, in geologic terms, because of fluctuations in carbon dioxide levels.”

We know from earlier study this year led by the Jet Propulsion Laboratory that polar ice sheet mass loss is speeding up and on pace for 1 foot sea level rise by 2050:

The Greenland and Antarctic ice sheets are losing mass at an accelerating pace, according to a new NASA-funded satellite study. The findings of the study — the longest to date of changes in polar ice sheet mass — suggest these ice sheets are overtaking ice loss from Earth’s mountain glaciers and ice caps to become the dominant contributor to global sea level rise, much sooner than model forecasts have predicted.

Recent modeling work suggests we are approaching the tipping point for irreversible melting of the Greenland ice sheet, which would, ultimately, represent 20 feet of sea level rise (see New study of Greenland under “more realistic forcings” concludes “collapse of the ice-sheet was found to occur between 400 and 560 ppm” of CO2).

And we know from paleoclimate studies that the Antarctic ice sheet (which contains 90% of the ice on the planet) is vulnerable to modest warming from current levels, particularly the West Antarctic Ice Sheet (see Science: CO2 levels haven’t been this high for 15 million years, when it was 5° to 10°F warmer and seas were 75 to 120 feet higher — “We have shown that this dramatic rise in sea level is associated with an increase in CO2 levels of about 100 ppm”).

While the new study  firms up our understanding that CO2 is the “main dial that governs global climate,” it does not appear to tell us what the tipping point is for full deglaciation:

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Global temperatures in 2011 are currently the tenth highest on record and are higher than any previous year with a La Niña event, which has a relative cooling influence. The 13 warmest years have all occurred in the 15 years since 1997. The extent of Arctic sea ice in 2011 was the second lowest on record, and its volume was the lowest.

“Our role is to provide the scientific knowledge to inform action by decision makers,” said [World Meteorological Organization] Secretary-General Michel Jarraud. “Our science is solid and it proves unequivocally that the world is warming and that this warming is due to human activities,” he said.

“Concentrations of greenhouse gases in the atmosphere have reached new highs. They are very rapidly approaching levels consistent with a 2-2.4 degree Centigrade rise in average global temperatures which scientists believe could trigger far reaching and irreversible changes in our Earth, biosphere and oceans,” he said.

That’s from the WMO news release highlighting the “provisional annual World Meteorological Organization Statement on the Status of the Global Climate, which gives a global temperature assessment and a snapshot of weather and climate events around the world in 2011.”

Here’s more:

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by Lauren Simenauer, cross posted from Science Progress

In the late 18th century, Benjamin Franklin was something of an icon in Europe. The French hung portraits of Franklin on their walls much in the same way college students pay tribute to John Belushi or Jim Morrison in their dorms. Everywhere Franklin went, his feisty personality preceded him, and it was this reputation in Europe that played a key role in securing the foreign aid the revolutionaries needed to triumph over the British. Many consider the celebrated polymath to be the first “American” in numerous regards—in entrepreneurialism, in political discourse, and, of course, in partying. As it turns out, Franklin was also the first American environmentalist, and his inventions influenced the scientific community for decades.

Energy Efficiency

In the age of clean energy technologies racing to meet grid parity, we often forget that there was a push for cleaner energy in the time of the founders. Ben Franklin himself designed a four-sided street lamp to replace the commonly used globe lamps. A build-up of soot darkened the globe lamps, which required near-daily cleaning, and let off an excess of smoke. The Franklin lamp increased air circulation within the lamps, allowing for better fuel efficiency and less cleaning.

Similarly, Franklin sought to design a more fuel-efficient stove that consumed less wood and produced more heat. Incidentally, though Franklin managed to sell multiple sets, the stove did not work very well. It was later improved upon, however, and has come to be known as the “Franklin Stove.”

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Back in February, a major study found that thawing permafrost feedback will turn Arctic from carbon sink to source in the 2020s, releasing 100 billion tons of carbon by 2100.  That study, by NOAA and the National Snow and Ice Data Center, conservatively assumed all of the carbon would be released as CO2 and none as the far more potent greenhouse gas, methane (CH4).

But that is unlikely, as this video of University of Alaska, Fairbanks, assistant professor Katey Walter Anthony, suggests:

A new article in Nature, “Climate change: High risk of permafrost thaw” (subs. req’d) concludes:

Arctic temperatures are rising fast, and permafrost is thawing…. Our collective estimate is that carbon will be released more quickly than models suggest, and at levels that are cause for serious concern.

We calculate that permafrost thaw will release the same order of magnitude of carbon as deforestation if current rates of deforestation continue. But because these emissions include significant quantities of methane, the overall effect on climate could be 2.5 times larger.

The permafrost permamelt contains a staggering amount of carbon, which is starting to escape:

Recent years have brought reports from the far north of tundra fires¹, the release of ancient carbon², CH₄ bubbling out of lakes³ and gigantic stores of frozen soil carbon⁴. The latest estimate is that some 18.8 million square kilometres of northern soils hold about 1,700 billion tonnes of organic carbon⁴ — the remains of plants and animals that have been accumulating in the soil over thousands of years. That is about four times more than all the carbon emitted by human activity in modern times and twice as much as is present in the atmosphere now.

As the article explains (see below), much of that carbon would be released as methane.  Methane is 25 times as potent a heat-trapping gas as CO2 over a 100 year time horizon, but 72 times to 100 times as potent over 20 years! 

The carbon is locked in a freezer in the part of the planet warming up the fastest (see “Tundra 4: Permafrost loss linked to Arctic sea ice loss“).  Countless studies make clear that global warming will release vast quantities of GHGs into the atmosphere this decade.  Yet, no climate model currently incorporates the amplifying feedback from methane released by a defrosting tundra.

The new analysis is based on a survey of “41 international scientists, listed as authors here, who publish on various aspects of permafrost.”  Yet even this new paper is conservative.  Their worst-case scenario appears to be derived from the out-of-date 2007 IPCC report, whereby Arctic warming “only” hits 7.5°C [13.5°F] by 2100.  And the new article further assumes temperature is then held constant for the next 200 years.

More recent analyses make clear that business-as-usual warming — not worst-case –  is likely to be considerably higher (see, for instance, “M.I.T. doubles its 2095 warming projection to 10°F — with 866 ppm and Arctic warming of 20°F“).  And the Earth would continue warming well past 2100, perhaps 50% to 100% more.

Even so, the new analysis finds the permafrost releases up to 380 billion tonnes of CO₂ equivalent by 2100.  This is comparable to the NOAA/NSIDC finding for this century, which looks like this:

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