RealClimate, a blog maintained by real climate scientists, is busy doing damage control. This story will no doubt rage for weeks, so I'm just going to pick one example of the back and forth before trying to take some time to go deeper, if merited.

Here's an e-mail that has gotten particular attention, with the supposedly damning language bolded:

Dear Ray, Mike and Malcolm,

Once Tim's got a diagram here we'll send that either later today or first thing tomorrow.

I've just completed Mike's Nature trick of adding in the real temps to each series for the last 20 years (ie from 1981 onwards) amd from 1961 for Keith's to hide the decline. Mike's series got the annual land and marine values while the other two got April-Sept for NH land N of 20N. The latter two are real for 1999, while the estimate for 1999 for NH combined is +0.44C wrt 61-90. The Global estimate for 1999 with data through Oct is +0.35C cf. 0.57 for 1998.

Thanks for the comments, Ray.

Cheers, Phil

Here's RealClimate's explanation:

The paper in question is the Mann, Bradley and Hughes (1998) Nature paper on the original multiproxy temperature reconstruction, and the "trick" is just to plot the instrumental records along with reconstruction so that the context of the recent warming is clear. Scientists often use the term "trick" to refer to a "a good way to deal with a problem", rather than something that is "secret", and so there is nothing problematic in this at all. As for the "decline," it is well known that Keith Briffa's maximum latewood tree ring density proxy diverges from the temperature records after 1960 (this is more commonly known as the "divergence problem" -- see e.g. the recent discussion in this paper) and has been discussed in the literature since Briffa et al in Nature in 1998 (Nature, 391, 678-682). Those authors have always recommend not using the post 1960 part of their reconstruction, and so while "hiding" is probably a poor choice of words (since it is "hidden" in plain sight), not using the data in the plot is completely appropriate, as is further research to understand why this happens.

So what's going on here? Put aside the question of whether the words "trick" or "hide" have nefarious or innocuous meanings. The scientific problem is that in attempting to reconstruct temperatures in the past, climate scientists are often faced with the problem that there were no humans standing around holding thermometers and writing down temperatures. So scientists use "proxies" -- tree rings, or ice cores, or fossilized clams, or lake pollen trapped in sediment. The "divergence problem" referred to above references a case where in one particular instance, tree ring variations in density did not match actual recorded temperatures after 1960.

That poses a conundrum, although not one that throws the entire science of multiproxy paleoclimate reconstruction into doubt.  More importantly, t the divergence problem, as RealClimate notes, is not a secret. It's exactly the kind of thing that climate scientists feast on. Such problems are discussed and debated every day by climate scientists (and every other kind of scientist.) The great thing about science is that the process of gathering  more data, improving models and theories is infinitely ongoing, and working out how to handle puzzlers like this, both in private e-mails and in the peer-reviewed literature, is what scientists live for.

Overall, the more data we have, the more clear it has become to the vast majority of scientists working in this field that the earth has gotten significantly hotter at an alarming rate in the last century, most likely due to increased concentrations of greenhouse gases in the atmosphere. And if there really is a smoking gun in the hacked e-mails that convicts scientists of fraudulent behavior or faking data, well, let's hear it. I'm not convinced by the above example. But if enough scientists are, that's a different matter.

I think Ollie's got his history a little mixed up. If I recall, Republicans, following the advice of consultant Frank Luntz, as formulated in his famous 2002 memo, started using the words "climate change" instead of "global warming" because global warming was "too frightening."

From an account in the UK Guardian:

The phrase "global warming" should be abandoned in favor of "climate change", Mr Luntz says, and the party should describe its policies as "conservationist" instead of "environmentalist", because "most people" think environmentalists are "extremists" who indulge in "some pretty bizarre behavior... that turns off many voters".

I guess one example of that bizarre behavior was a little semiotic jujitsu, in which environmentalists embraced the climate change name switch, but tacked on catastrophic to get the original point across.

Ironically, climate change appears to have stalled in the run-up to the upcoming world summit in the Danish capital, where thousands of politicians, bureaucrats, scientists, business leaders and environmental activists plan to negotiate a reduction in greenhouse gas emissions. Billions of euros are at stake in the negotiations.

Reached a plateau

The planet's temperature curve rose sharply for almost 30 years, as global temperatures increased by an average of 0.7 degrees Celsius (1.25 degrees Fahrenheit) from the 1970s to the late 1990s. "At present, however, the warming is taking a break," confirms meteorologist Mojib Latif of the Leibniz Institute of Marine Sciences in the northern German city of Kiel. Latif, one of Germany's best-known climatologists, says that the temperature curve has reached a plateau. "There can be no argument about that," he says. "We have to face that fact."

Even though the temperature standstill probably has no effect on the long-term warming trend, it does raise doubts about the predictive value of climate models, and it is also a political issue. For months, climate change skeptics have been gloating over the findings on their Internet forums. This has prompted many a climatologist to treat the temperature data in public with a sense of shame, thereby damaging their own credibility.

"It cannot be denied that this one of the hottest issues in the scientific community," says Jochem Marotzke, director of the Max Planck Institute for Meteorology in Hamburg. "We don't really know why this stagnation is taking place at this point."

Just a few weeks ago, Britain's Hadley Centre for Climate Prediction and Research added more fuel to the fire with its latest calculations of global average temperatures. According to the Hadley figures, the world grew warmer by 0.07 degrees Celsius from 1999 to 2008, and not by the 0.2 degrees Celsius assumed by the United Nations Intergovernmental Panel on Climate Change. And, say the British experts, when their figure is adjusted for two naturally occurring climate phenomena, El Niño and La Niña, the resulting temperature trend is reduced to 0.0 degrees Celsius -- in other words, a standstill.

The differences among individual regions of the world are considerable. In the Arctic, for example, temperatures rose by almost three degrees Celsius, which led to a dramatic melting of sea ice. At the same time, temperatures declined in large areas of North America, the western Pacific and the Arabian Peninsula. Europe, including Germany, remains slightly in positive warming territory.

Mixed messages

But a few scientists simply refuse to believe the British calculations. "Warming has continued in the last few years," says Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research (PIK). However, Rahmstorf is more or less alone in his view. Hamburg Max Planck Institute scientist Jochem Marotzke, on the other hand, says: "I hardly know any colleagues who would deny that it hasn't gotten warmer in recent years."

The controversy sends confusing and mixed messages to the lay public. Why is there such a vigorous debate over climate change, even though it isn't getting warmer at the moment? And how can it be that scientists cannot even arrive at a consensus on changes in temperatures, even though temperatures are constantly being measured?

The global temperature-monitoring network consists of 517 weather stations. But each reading is only a tiny dot on the big world map, and it has to be extrapolated to the entire region with the help of supercomputers. Besides, there are still many blind spots, the largest being the Arctic, where there are only about 20 measuring stations to cover a vast area. Climatologists refer to the problem as the "Arctic hole."

The scientists at the Hadley Center simply used the global average value for the hole, ignoring the fact that it has become significantly warmer in the Arctic, says Rahmstorf. But a NASA team from the Goddard Institute for Space Studies in New York, which does make the kinds of adjustments for the Arctic data that Rahmstorf believes are necessary, arrives at a flat temperature curve for the last five years that is similar to that of their British colleagues.

Marotzke and Leibniz Institute meteorologist Mojib Latif are even convinced that the fuzzy computing done by Rahmstorf is counterproductive. "We have to explain to the public that greenhouse gases will not cause temperatures to keep rising from one record temperature to the next, but that they are still subject to natural fluctuations," says Latif. For this reason, he adds, it is dangerous to cite individual weather-related occurrences, such as a drought in Mali or a hurricane, as proof positive that climate change is already fully underway.

"Perhaps we suggested too strongly in the past that the development will continue going up along a simple, straight line. In reality, phases of stagnation or even cooling are completely normal," says Latif.

Part 2: The difficulties of predicting the climate

Climatologists use their computer models to draw temperature curves which continue well into the future. They predict that the average global temperature will increase by about three degrees Celsius (5.4 degrees Fahrenheit) by the end of the century, unless humanity manages to drastically reduce greenhouse gas emissions. However, no one really knows what exactly the world climate will look like in the not-so-distant future, that is, in 2015, 2030 or 2050.

This is because it is not just human influence but natural factors that affect the Earth's climate. For instance, currents in the world's oceans are subject to certain cycles, as is solar activity. Major volcanic eruptions can also curb rising temperatures in the medium term. The eruption of Mount Pinatubo in June 1991, for example, caused world temperatures to drop by an average of 0.5 degrees Celsius, thereby prolonging a cooler climate phase that had begun in the late 1980s.

But the Mount Pinatubo eruption happened too long ago to be related to the current slowdown in global warming. So what is behind this more recent phenomenon?

Weaker solar activity

The fact is that the sun is weakening slightly. Its radiation activity is currently at a minimum, as evidenced by the small number of sunspots on its surface. According to calculations performed by a group of NASA scientists led by David Rind, which were recently published in the journal Geophysical Research Letters, this reduced solar activity is the most important cause of stagnating global warming.

Latif, on the other hand, attributes the stagnation to so-called Pacific decadal oscillation (PDO). This phenomenon in the Pacific Ocean allows a larger volume of cold deep-sea water to rise to the surface at the equator. According to Latif, this has a significant cooling effect on the Earth's atmosphere.

With his team at the Leibniz Institute of Marine Sciences, Latif has been one of the first to develop a model to create medium-term prognoses for the next five to 10 years. "We are slowly starting to attempt (such models)," says Marotzke, who is also launching a major project in this area, funded by the Federal Ministry for Research and Technology.

Despite their current findings, scientists agree that temperatures will continue to rise in the long term. The big question is: When will it start getting warmer again?

If the deep waters of the Pacific are in fact the most important factor holding up global warming, climate change will remain at a standstill until the middle of the next decade, says Latif. But if the cooling trend is the result of reduced solar activity, things could start getting warmer again much sooner. Based on past experience, solar activity will likely increase again in the next few years.

Betting on warmer temperatures

The Hadley Center group expects warming to resume in the coming years. "That resumption could come as a bit of a jolt," says Hadley climatologist Adam Scaife, explaining that natural cyclical warming would then be augmented by the warming effect caused by anthropogenic greenhouse gas emissions.

While climatologists at conferences engage in passionate debates over when temperatures will start rising again, global warming's next steps have also become the subject of betting activity.

Climatologist Stefan Rahmstorf is so convinced that his predictions will be correct in the end that he is willing to back up his conviction with a €2,500 ($3,700) bet. "I will win," says Rahmstorf.

His adversary Latif turned down the bet, saying that the matter was too serious for gambling. "We are scientists, not poker players."

Translated from the German by Christopher Sultan

Great Basin bristlecone pine (Pinus longaeva) at 3 sites in western North America near the upper elevation limit of tree growth showed ring growth in the second half of the 20th century that was greater than during any other 50-year period in the last 3,700 years. The accelerated growth is suggestive of an environmental change unprecedented in millennia.

RealClimate offers an accessible summary. Bristlecone pines are quite popular with paleoclimatologists who specialize in analyzing tree rings because they live for thousands of years. The bottom line -- in recent decades, bristlecones have responded dramatically to warmer temperatures.

Meanwhile, from Europe comes the news that wine-makers are stressing out about global warming.

From AFP:

"All over the world, alcohol levels are going up," said British wine critic Jancis Robinson at the WineFuture conference, citing just one problem producers are facing as a result of rising temperatures.

"Champagne alcohol levels are becoming embarrassingly high," she added, meaning that the heat which is raising the alcohol content changes both the texture and personality of a wine.

One answer for wineries: Just as the Western Bristlecone will likely respond to higher temperatures by spreading to higher elevations in a natural example of adaptation, wineries too could move north to milder regions as temperatures rise. Of course, if that happens, we would no longer be able to call champagne by the name "champagne," since the grapes would no longer be grown in the province of Champagne. But that's quibbling! Why worry about global warming? Just like the bristlecone, we'll just move on up.

There is no question that humanity will adapt to climate change. Even if the climate bill of an environmentalist's dreams were enacted into law tomorrow, we're not going to stop rising temperatures in the near future. The best we can legitimately hope to do, at this point, is slow the rise. So along with cutting back greenhouse gas emissions and using energy more efficiently, we will also be forced to adapt. And maybe the tundra will bloom with corn and Norway will be pumping out faux-Bordeaux.

But there are degrees of adaptation. For example, after a hurricane-propelled storm surge wipes out your beachfront home, you might decide to move inland. A little costly, a little risky, perhaps, but hey, you're adapting. But what if you decided to move before your house was destroyed? Or what if, even better, your society cut back on greenhouse gas emissions enough so that sea temperatures didn't rise quite so quickly, giving you more time to figure out whether you wanted to move, or build a stronger house, or erect a sea wall?

One of the key things that separates humans from most other animals is that our brains feature highly developed frontal lobes that enable us to think about the future and take proactive action to ward off misfortune. A bristlecone pine or a grapevine can't do that. But we can. We can adapt the hard way, by letting climate change wreak havoc, or the easy way, by doing what we can to give us more of a chance to properly adapt -- and maybe, just maybe, keep champagne in Champagne.

As one might guess, in 1970, the center of Co2 emissions gravity was located between Europe and the United States, just off the coast of Iceland. Since then it has moved steadily to the east, toward Asia. More troublingly, the rate at which greenhouse gas emissions are moving is faster than the rate at which the center of GDP growth is moving, suggesting that "Asian production is getting more CO2 intensive than Western production." That's not good news, because it means that industrial production is getting less efficient and worse for the environment as it migrates to Asia.

A side note: The satellite photos of the globe with their little pink and yellow balloons superimposed on the planet emphasize, quite strongly, the truth of North-South relations, at least insofar as industrial production is concerned. Because the center of gravity may be moving on the East-West axis at a brisk pace, but it's going absolutely nowhere on the North-South axis. If I lived in the South, I'd know whom to blame for climate change.