A prominent climate change skeptic told Congress on Monday he no longer doubts that global warming is real and caused by humans, and joined other scientists in urging action to stop it.
Physicist Richard Muller, director of the Berkeley Earth Surface Temperature Project, whose two-year research was funded in part by a foundation formed by the conservative billionaire Koch brothers, said he could find no bias in other studies.
"We confirm that over the last 50 years, temperature has risen 0.9 degrees Celsius, or 1.6 degrees Fahrenheit. This is the same number that the IPCC (UN Intergovernmental Panel on Climate Change) says."
Muller told the House Committee on Natural Resources that while he remains cautious about the extent to which humans have played a role, he now hopes other climate skeptics will come on board with his findings.
"As they read and study our papers, I am hoping that many of them will reflect my belief that they are open-minded and come to agree that yes, climate change temperature increase certainly has happened," he said.

2011 Among Hottest Years, Marked by Extreme Weather
Not even cooling La Niña could take edge off warming trend.



A rendering shows Arctic sea ice.
An animation still using satellite data shows Arctic sea ice melt during the summer of 2011.

Image courtesy SVS/NASA

Richard A. Lovett

for National Geographic News

Published November 30, 2011

This year is shaping up to be one of the ten hottest years on record, according to a United Nations report announced yesterday.

Likewise, 2011 may be the hottest year on record during La Niña, a periodic cooling of the eastern tropical Pacific.

That's a bad sign, since La Niña years are generally relatively cool, said Steven Running, a professor of ecology at the University of Montana, who was not part of the study team.

So the new finding suggests that La Niña conditions that once produced strong global cooling now only slightly affect the overall temperature trend, Running said by email.

"What does it take now to have a cooling cycle?" he asked. "And what will happen in the next strong El Niño?"

El Niño is a warming of tropical waters in the central and eastern Pacific Ocean. During El Niño years, the warmer currents heat the planet on top of the steady global warming trend caused by human-induced greenhouse gases.

Based on data from 189 countries, the World Meteorological Organization (WMO) report was presented at an international climate conference this week in Durban, South Africa.

(Related: "Global Warming 'Marches On'; Past Decade Hottest Known.")

Climate Hot, and Getting Hotter

The report also found that all but two of the overall 15 hottest years since record-keeping began in 1850 have occurred between 1997 and 2011. (See "Heat Wave: 2010 to Be One of Hottest Years on Record.")

In addition, sea ice coverage was the second lowest on record. The lowest occurred in 2007.

Even that figure might be deceptively optimistic, because much of the sea ice appears to have been thinner than in past years. When sea ice cover was at its smallest in 2011, on September 9, the total Arctic sea ice volume was 8 percent lower than in 2010—previously the lowest on record, the WMO scientists found.

(See "Global Warming Silver Lining? Arctic Could Get Cleaner.")

The WMO's Global Atmosphere Watch program also recently released a report concluding that heat-trapping greenhouse gases in the atmosphere had reached a new high—an increase that will only continue, researchers say.

"Our science is solid, and it proves unequivocally that the world is warming and that this warming is due to human activities," WMO Secretary-General Michel Jarraud said in a statement addressing both reports.

(Quiz: Test your global warming knowledge.)

Floods, Droughts: A Year of Climate Extremes

This year was also full of extremes, according to this week's report.

Not surprisingly, given the high rates of melting in the Arctic, many Arctic regions were unusually hot. Parts of northern Russia reported springtime temperatures more than 16°F (9°C) above average, the WMO said.

(Related blog post: "Russia Burns in Hottest Summer on Record [2010].")

But there was plenty of other extreme weather elsewhere. For instance:

* Finland, Armenia, Central America, and Spain all reported record heat.

* It was the driest spring on record in many parts of western Europe, followed in some areas by the wettest summer.

* East Africa experienced severe drought followed by flooding.

* Other severe floods, often deadly, occurred in Southeast Asia, Brazil, Australia, Southern Africa, Central America, and Pakistan. (Read: "Extreme Storms and Floods Concretely Linked to Climate Change?")

* Tropical cyclone and hurricane activity was unusually low, although not as low as in 2010 (which had the lowest storm count since satellites first allowed accurate record keeping).

(See a world map of potential global warming impacts.)

Texas-Size Temperature Rise

Extremes were also present in the U.S. and Canada, where conditions ranged from drought and heat in the South to heavy snowpack in the Midwest to record-breaking rainfall in the Northeast.

It was also the third worst U.S. tornado season since 1950, after 2004 and 2008.

(Read "Monster Alabama Tornado Spawned by Rare 'Perfect Storm.'")

But the most stunning figures may have come from Texas, where daily temperatures averaged 86.7° (30.4°C), in June through August—a staggering 5.4°F (3.0°C) above normal, scientists said.

The Texas statistic is "the highest [such average] ever recorded for any American state," according to the WMO website.

It's difficult to determine exactly how much of the extremes are due to climate change versus normal weather variations, said Richard Alley, a geoscientist at Pennsylvania State University, who was not part of the WMO team.

"The increasing carbon dioxide and other greenhouse gases in the air from our activities do not make 'weather' disappear," he said by email. "But they do 'load the dice' to make hot conditions more likely.

"We haven't made cold snaps, and even record lows, disappear, but data and our physical understanding agree that we're still pushing strongly toward warming."

http://news.nationalgeographic.com/news ... vironment/

Katey M. Walter Anthony, a scientist, investigated a plume of methane, a greenhouse gas, at an Alaskan lake. Dr. Walter Anthony is a leading researcher in studying the escape of methane.

Temperature Rising
As Permafrost Thaws, Scientists Study the Risks

Dr. Walter Anthony had already run chemical tests on the methane from one of the lakes, dating the carbon molecules within the gas to 30,000 years ago. She has found carbon that old emerging at numerous spots around Fairbanks, and carbon as old as 43,000 years emerging from lakes in Siberia.

“These grasses were food for mammoths during the end of the last ice age,” Dr. Walter Anthony said. “It was in the freezer for 30,000 to 40,000 years, and now the freezer door is open.”

Edward A. G. Schuur, a University of Florida researcher who has done extensive field work in Alaska, is worried by the changes he already sees, including the discovery that carbon buried since before the dawn of civilization is now escaping.

“To me, it’s a spine-tingling feeling, if it’s really old carbon that hasn’t been in the air for a long time, and now it’s entering the air,” Dr. Schuur said. “That’s the fingerprint of a major disruption, and we aren’t going to be able to turn it off someday.”

2011 was the second warmest year on record in Britain, the Met Office national weather service has said, a marked swing from a chillier 2010.

Provisional figures showed that the average temperature throughout the year was 9.62 degrees Celsius (49.3 degrees Fahrenheit).

The record high is still 2006, which notched an average temperature of 9.73 C (49.5 F).

All but one of the top 10 warmest years on record have occurred since 1997 and all Britain's top seven warmest years happened in the last decade.

<SNIP>

The 2011 Winner: Climate B.S. from all of the Republican candidates for President of the United States

Second Place: Disinformation from Fox News and Murdoch’s News Corporation

Third Place: Spencer, Braswell, and Christy for their lack of climate “sensitivity”

Fourth Place: The Koch Brothers for funding the promotion of bad climate science

Fifth Place: Anthony Watts for his BEST, and worst, climate hypocrisy

The Amazon Basin, traditionally considered a bulwark against global warming, may be becoming a net contributor of carbon dioxide (CO2) as a result of deforestation, researchers said on Wednesday.
In an overview published in the journal Nature, scientists led by Eric Davidson of the Woods Hole Research Center in Massachusetts say the Amazon is "in transition" as a result of human activity.
Over 50 years, the population has risen from six million to 25 million, triggering massive land clearance for logging and agriculture, they said.
The Amazon's carbon budget -- the amount of CO2 that it releases into the atmosphere or takes from it -- is changing although it is hard to estimate accurately, they said.
"Deforestation has moved the net basin-wide budget away from a possible late 20th-century net carbon sink and towards a net source," according to their paper.

Nine of the top ten warmest years in the modern meteorological record have occurred since the year 2000. Last year was another one of them, coming in at 9th warmest since 1880.

Do you consult your dentist about your heart condition? In science, as in any area, reputations are based on knowledge and expertise in a field and on published, peer-reviewed work. If you need surgery, you want a highly experienced expert in the field who has done a large number of the proposed operations.

You published “No Need to Panic About Global Warming” (op-ed, Jan. 27) on climate change by the climate-science equivalent of dentists practicing cardiology. While accomplished in their own fields, most of these authors have no expertise in climate science. The few authors who have such expertise are known to have extreme views that are out of step with nearly every other climate expert. This happens in nearly every field of science. For example, there is a retrovirus expert who does not accept that HIV causes AIDS. And it is instructive to recall that a few scientists continued to state that smoking did not cause cancer, long after that was settled science.

Climate experts know that the long-term warming trend has not abated in the past decade. In fact, it was the warmest decade on record. Observations show unequivocally that our planet is getting hotter. And computer models have recently shown that during periods when there is a smaller increase of surface temperatures, warming is occurring elsewhere in the climate system, typically in the deep ocean. Such periods are a relatively common climate phenomenon, are consistent with our physical understanding of how the climate system works, and certainly do not invalidate our understanding of human-induced warming or the models used to simulate that warming.

cont...

The Global Warming Policy Foundation (GWPF) is a British political think tank that attacks climate science. Its commentary is often regurgitated by journalists at newspapers with similar political opinions on climate science such as the Daily Mail, Express and Telegraph (whose consulting science editor is a GWPF adviser).

The Daily Mail recently published an article covering two bits of science news. One is that the UK Met Office and their partners are updating their global temperature data and including more measurements from Russia and around the Arctic. The data aren't publicly available yet, but graphs from a Met Office presentation suggest that 2005 and 2010 could be warmer than the previous record holder (1998), bringing the British data into agreement with NASA and the National Climatic Data Centre.

The other bit of science news is research on how the Sun is expected to cool down slightly in the coming decades. "The likely reduction in the warming by 2100 is found to be between 0.06 and 0.1K" (Jones, Lockwood & Stott, 2012), much less than the 0.17 C warming per decade measured since the 1970s (1 K is the same size as 1 degree Celsius).

Gareth Jones, the climate science expert who led the Met Office research said "this research shows that the most likely change in the Sun's output will not have a big impact on global temperatures or do much to slow the warming we expect from greenhouse gases."

The Daily Mail's interpretation is the opposite of what the scientists reported, and dutifully parrots GWPF talking points. The article claims we're possibly heading for a "mini ice age", that there has been "no warming for 15 years" and quotes the GWPF's Benny Peiser's prophecies of doom for climate models.

rest of the article

Evaluating a 1981 temperature projection
Filed under:

* Climate modelling
* Climate Science
* Greenhouse gases
* Instrumental Record

— group @ 2 April 2012

Guest commentary from Geert Jan van Oldenborgh and Rein Haarsma, KNMI

Sometimes it helps to take a step back from the everyday pressures of research (falling ill helps). It was in this way we stumbled across Hansen et al (1981) (pdf). In 1981 the first author of this post was in his first year at university and the other just entered the KNMI after finishing his masters. Global warming was not yet an issue at the KNMI where the focus was much more on climate variability, which explains why the article of Hansen et al. was unnoticed at that time by the second author. It turns out to be a very interesting read.

They got 10 pages in Science, which is a lot, but in it they cover radiation balance, 1D and 3D modelling, climate sensitivity, the main feedbacks (water vapour, lapse rate, clouds, ice- and vegetation albedo); solar and volcanic forcing; the uncertainties of aerosol forcings; and ocean heat uptake. Obviously climate science was a mature field even then: the concepts and conclusions have not changed all that much. Hansen et al clearly indicate what was well known (all of which still stands today) and what was uncertain.

Next they attribute global mean temperature trend 1880-1980 to CO2, volcanic and solar forcing. Most interestingly, Fig.6 (below) gives a projection for the global mean temperature up to 2100. At a time when the northern hemisphere was cooling and the global mean temperature still below the values of the early 1940s, they confidently predicted a rise in temperature due to increasing CO2 emissions. They assume that no action will be taken before the global warming signal will be significant in the late 1990s, so the different energy-use scenarios only start diverging after that.



The first 31 years of this projection are thus relatively well-defined and can now be compared to the observations. We used the GISS Land-Ocean Index that uses SST over the oceans (the original one interpolated from island stations) and overlaid the graph from the KNMI Climate Explorer on the lower left-hand corner of their Fig.6.



Given the many uncertainties at the time, notably the role of aerosols, the agreement is very good indeed. They only underestimated the observed trend by about 30%, similar or better in magnitude than the CMIP5 models over the same period (although these tend to overestimate the trend, still mainly due to problems related to aerosols).

To conclude, a projection from 1981 for rising temperatures in a major science journal, at a time that the temperature rise was not yet obvious in the observations, has been found to agree well with the observations since then, underestimating the observed trend by about 30%, and easily beating naive predictions of no-change or a linear continuation of trends. It is also a nice example of a statement based on theory that could be falsified and up to now has withstood the test. The “global warming hypothesis” has been developed according to the principles of sound science.

Macdoc wrote:Great look back from RealClimate -

New Report On the State of Polar Regions

ScienceDaily (Apr. 3, 2012) — The U.S. National Research Council has just released a synthesis of reports from thousands of scientists in 60 countries who took part in the International Polar Year (IPY) 2007-08, the first in over 50 years to offer a benchmark for environmental conditions and new discoveries in the polar regions.

University of Massachusetts Amherst geosciences researcher and expert in the paleoclimate of the Arctic, Julie Brigham-Grette, co-chaired the NRC report, "Lessons and Legacies of the IPY 2007-08" with leading Antarctic climate scientist Robert Bindschadler of NASA.

Among the major findings is that global warming is changing the face of Antarctica and the Arctic faster than expected. For example, in 2007 scientists documented a 27 percent loss of sea ice in a single year, Brigham-Grette says. Also, ice sheets around the poles are now showing evidence of serious retreat, expected to continue and perhaps accelerate over coming centuries as warm ocean currents melt the ice front faster than anyone had grasped before. Sea level rise from melting polar ice sheets is today slowly affecting every shoreline on the planet.

"As a result of this work, we have a new benchmark. Seven of 12 Antarctic Peninsula ice shelves are either gone or now in severe decline," she adds. "This type of information makes the report all the more important because the changes we expect to see in the next few decades are going to be incredible."

As co-authors, she and Bindschadler testified last week before representatives of the National Science Foundation, its Office of Polar Programs, NASA, NOAA, the U.S. Geological Survey, Office of Naval Research, the State Department and the U.S. Arctic Research Commission. Additional briefings could be scheduled if there are questions or responses to the NRC from Congress, Brigham-Grette says.

Worldwide, scores of oceanographers, meteorologists, geologists, climate scientists, ecologists and other researchers contributed to the report. For example, biologists document diatoms, microscopic phytoplankton at the base of the food chain, in North Atlantic waters where they hadn't been in 800,000 years, the last time the Arctic provided a cold barrier to migration, Brigham-Grette says. Fish specialists see commercial and other species migrating ever northward to suitable habitats. "The fishermen are following," she says. "It's a whole new ballgame for the U.S. Coast Guard and those trying to regulate harvests."

The UMass Amherst geoscientist's own research using ancient sediment cores from Northeast Russia's Lake El'gygytgyn offers a new look at how Antarctic and Arctic warming over the last few million years occurred in sync when forced by the Earth system and feedbacks. "We're beginning to see that when the west Antarctic ice sheet collapses, the Arctic warms up. This is a new benchmark linking warming events in these two places for the first time."

In the Antarctic, new imaging techniques deployed during the recent IPY allowed scientists for the first time to visualize a new range, the Gamburtsev Mountains, with peaks as big as the Alps under the east Antarctic ice sheet. They may have been the ice sheet's nucleus millions of years ago. Others found hundreds of freshwater lakes under Antarctic ice, with more being discovered every day.

Brigham-Grette says, "I think if you look at everything we've learned, we see the polar regions are much more vulnerable to global warming than we thought. Global biological and oceanographic systems are responding faster than we ever expected. Earth has gone through this before, and some past warm cycles have been extreme, but we as humans have never seen anything like it in our 10,000 years on the planet. It's extraordinary."

As they release the NRC report to policymakers this week, Brigham-Grette says the authors understand that leaders must try to balance the country's energy needs at the same time they address global climate change by decreasing fossil fuel use.

Two social advances to emerge from the recent IPY are a remarkable increase in the number of women and minorities in leadership roles in science compared to 50 years ago along with the "massive" educational effort and increased interest in and public awareness of issues facing polar regions, she adds.

Among scientists, the IPY led to many new international and multi-disciplinary collaborations that promise to continue, says Brigham-Grette, plus a new international network of young polar scientists. "With the expense of travel and research today, no one country can do it alone, so there's more sharing of resources and data. It's a very much richer environment for study today."

University of Massachusetts Amherst (2012, April 3). New report on the state of polar regions. ScienceDaily. Retrieved April 5, 2012, from http://www.sciencedaily.com­ /releases/2012/04/120403193733.htm

Advanced power-grid research finds low-cost, low-carbon future in West
April 3, 2012




One possible scenario for the electricity system in the Western US in 2026-29. Pie charts show the proportion of different types of energy sources generating power and flowing between load areas if there were a carbon tax of $70 per ton. According to the SWITCH model, such a tax could allow the West to reach a goal of 54 percent of 1990 emissions by 2030. Credit: Daniel Kammen lab, UC Berkeley

The least expensive way for the Western U.S. to reduce greenhouse gas emissions enough to help prevent the worst consequences of global warming is to replace coal with renewable and other sources of energy that may include nuclear power, according to a new study by University of California, Berkeley, researchers.

The experts reached this conclusion using SWITCH, a highly detailed computer model of the electric power grid, to study generation, transmission and storage options for the states west of the Kansas/Colorado border. The model will be an important tool for utilities and government planners.

"Decarbonization of the electric power sector is critical to achieving greenhouse gas reductions that are needed for a sustainable future," said Daniel Kammen, Distinguished Professor of Energy in UC Berkeley's Energy and Resources Group. "To meet these carbon goals, coal has to go away from the region."

One example of low-cost, low-carbon energy generation and transmission around the West by 2030.

One possible scenario for the electricity system in the Western U.S. in 2026-29. Pie charts show the proportion of different types of energy sources generating power and flowing between load areas if there were a carbon tax of $70 per ton. According to the SWITCH model, such a tax could allow the West to reach a goal of 54% of 1990 emissions by 2030.

To achieve this level of decarbonization, policy changes are needed to cap or tax carbon emissions to provide an incentive to move toward low-carbon electricity sources, Kammen and the other study authors said.

While some previous studies have emphasized the high cost of carbon taxes or caps, the new study shows that replacing coal with more gas generation, as well as renewable sources like wind, solar and geothermal energy, would result in only a moderate increase to consumers in the cost of electric power – at most, 20 percent. They estimate a lower ratepayer cost, Kammen said, because the evolution of the electrical grid over the next 20 years – with coordinated construction of new power plants and transmission lines – would substantially reduce the actual consumer cost of meeting carbon emission targets.

"While the carbon price required to induce these deep carbon emission reductions is high – between $59 and $87 per ton of CO2 emitted – the cost of power is predicted to increase by at most 20 percent, because the electricity system will redesign itself around a price or cap on carbon emissions," said Kammen. "That is a modest cost considering that the future of the planet is at stake."

Coal hazards

Burning coal, a non-renewable resource, produces about 20 percent of the world's greenhouse gases, but also releases harmful chemicals into the environment such as mercury, sulfur dioxide, nitrogen oxides and sulfuric acid, responsible in some areas for acid rain and respiratory illness.

California has few coal-fired power plants, but gets about 20 percent of its electricity from coal-burning plants in neighboring states. About 46 percent of the state's power comes from gas-burning plants, 11 percent from hydroelectric, 14 percent from nuclear and 11 percent from other renewables: geothermal energy, wind and solar.

The study, published in the April issue of the journal Energy Policy, highlights an analysis using the SWITCH electricity planning model. SWITCH, which stands for Solar, Wind, Hydro and Conventional generation and Transmission Investment, uses unprecedented detail that includes generation, transmission and storage of electricity. The model was developed by Matthias Fripp to study California's renewable energy options while he was a Ph.D. student at UC Berkeley. Kammen and his group extended the model's capabilities and used it to study Western North America.

"We use the SWITCH model to identify low-carbon supply options for the West, and to see how intermittent generation may be deployed in the future," said first author James Nelson, a UC Berkeley graduate student. "We show that it is possible to reach our goals of reducing carbon emissions using many possible mixes of power, whether natural gas, nuclear, solar, wind, biomass or geothermal."

"Models like this are eagerly anticipated by many of the agencies involved in planning," Kammen said, noting that SWITCH is a power-system model that can be fine-tuned for many different types of studies.

Setting targets for 2030 emissions

Mandates called Renewable Portfolio Standards (RPS) currently dominate carbon reduction policy in the United States. These standards require that a certain fraction of electricity generation come from renewable sources. While California has a relatively high RPS target of 33 percent renewable sources by 2020, other Western states have less ambitious targets. Additional policy action throughout Western North America will be required to meet climate targets, Kammen said.

The UC Berkeley study concluded that current RPS targets are not sufficient to put electric power sector emissions on track to limit atmospheric levels of carbon to less than 450 ppm, a climate stabilization target recommended by the Intergovernmental Panel on Climate Change. That target requires carbon emissions from electricity production in industrialized countries to drop to no more than 54 percent of 1990 emissions by 2030.

However, the study finds that the right mix of renewable energy sources can meet climate goals given stronger carbon policy.

Of all 50 states, California has been the most aggressive in setting goals for reducing carbon emissions, with a target to return to 1990 levels by 2020. The first step along the path of changing the balance of energy sources is the establishment of a carbon trading market in California, which will be up and running in September 2012, said Kammen.

Provided by University of California - Berkeley

It's already been a very record-breaking hot year
April 9, 2012 By SETH BORENSTEIN , AP Science Writer

The lower 48 states were 8.6 degrees above normal for March and 6 degrees higher than average for the first three months of the year, according to calculations by the National Oceanic and Atmospheric Administration, with both March and the first three months of the year far exceeding the country’s old records.(AP Photo/David Goldman)

(AP) -- It's been so warm in the United States this year, especially in March, that national records weren't just broken, they were deep-fried.
Temperatures in the lower 48 states were 8.6 degrees above normal for March and 6 degrees higher than average for the first three months of the year, according to calculations by the National Oceanic and Atmospheric Administration. That far exceeds the old records.

The magnitude of how unusual the year has been in the U.S. has alarmed some meteorologists who have warned about global warming. One climate scientist said it's the weather equivalent of a baseball player on steroids, with old records obliterated.

"Everybody has this uneasy feeling. This is weird. This is not good," said Jerry Meehl, a climate scientist who specializes in extreme weather at the National Center for Atmospheric Research in Boulder, Colo. "It's a guilty pleasure. You're out enjoying this nice March weather, but you know it's not a good thing."

It's not just March.

"It's been ongoing for several months," said Jake Crouch, a climate scientist at NOAA's National Climatic Data Center in Ashville, N.C.

Meteorologists say an unusual confluence of several weather patterns, including La Nina, was the direct cause of the warm start to 2012. While individual events can't be blamed on global warming, Couch said this is like the extremes that are supposed to get more frequent because of manmade climate change from the burning of fossil fuels such as coal and oil.

It's important to note that this unusual winter heat is mostly a North America phenomenon. Much of the rest of the Northern Hemisphere has been cold, said NOAA meteorologist Martin Hoerling.

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The first quarter of 2012 broke the January-March record by 1.4 degrees. Usually records are broken by just one- or two-tenths of a degree. U.S. temperature records date to 1895.

The atypical heat goes back even further. The U.S. winter of 2010-2011 was slightly cooler than normal and one of the snowiest in recent years, but after that things started heating up. The summer of 2011 was the second warmest summer on record.

The winter that just ended, which in some places was called the year without winter, was the fourth warmest on record. Since last April, it's been the hottest 12-month stretch on record, Crouch said.

But the month where the warmth turned especially weird was March.

Normally, March averages 42.5 degrees across the country. This year, the average was 51.1, which is closer to the average for April. Only one other time - in January 2006 - was the country as a whole that much hotter than normal for an entire month.

The "icebox of America," International Falls, Minn., saw temperatures in the 70s for five days in March, and there were only three days of below zero temperatures all month.

In March, at least 7,775 weather stations across the nation broke daily high temperature records and another 7,517 broke records for night-time heat. Combined, that's more high temperature records broken in one month than ever before, Crouch said.

"When you look at what's happened in March this year, it's beyond unbelievable," said University of Victoria climate scientist Andrew Weaver.

NOAA climate scientist Gabriel Vecchi compared the increase in weather extremes to baseball players on steroids: You can't say an individual homer is because of steroids, but they are hit more often and the long-held records for home runs fall.

They seem to be falling far more often because of global warming, said NASA top climate scientist James Hansen. In a paper he submitted to the journal Proceedings of the National Academy of Sciences and posted on a physics research archive, Hansen shows that heat extremes aren't just increasing but happening far more often than scientists thought.

What used to be a 1-in-400 hot temperature record is now a 1 in 10 occurrence, essentially 40 times more likely, said Hansen. The warmth in March is an ideal illustration of this, said Hansen, who also has become an activist in fighting fossil fuels.

Weaver, who reviewed the Hansen paper, called it "one of the most stunning examples of evidence of global warming."