BEST: 1½ °C stigning i globale landtemperaturer siden 1750

29. juli 2012

I går aftes tikkede følgende pressemeddelelse ind fra Berkelys BEST-projekt:

“Berkeley Earth has just released new results, showing that the average temperature of the Earth’s land has risen by 1.5°C over the past 250 years. The good match between the new temperature record and historical carbon dioxide records suggests that the most straightforward explanation for this warming is human greenhouse gas emissions.

The new analysis from Berkeley Earth goes all the way back to 1753, about 100 years earlier than previous groups’ analysis.  The limited land coverage prior to 1850 results in larger uncertainties in the behavior of the record; despite these, the behavior is significant. Sudden drops in the early temperature record (1750 to 1850) correspond to known volcanic events.

In its 2007 report the IPCC concluded only that “most” of the warming of the past 50 years could be attributed to humans. It was possible, according to the IPCC, that increased solar activity could have contributed to warming prior to 1956.  Berkeley Earth analyzed about 5 times more station records than were used in previous analyses, and this expanded data base along with its new statistical approach allowed Berkeley Earth to go about 100 years farther back in time than previous studies.  By doing so, the Berkeley Earth team was able to conclude that over 250 years, the contribution of solar activity to global warming is negligible.”

Når dette er et interessant resultat, er det ikke så meget fordi BEST-projektet afdækker noget nyt, som fordi det er defineret og gennemført under ledelse af Richard A. Muller, som har været erklæret skeptiker, for at vise, at klimavidenskaben var galt afmarcheret i sit helt grundlæggende talmateriale, nemlig målingerne af temperaturen ved jordens overflade.

En af BEST-projektets sponsorer er således Koch Industries, som er en af de store bidragydere til den organiserede tvivlsproduktion gennem enheder som heartland Institute. Men Muller har samtidig med den nuværende fremlæggelse talt om a “full turnaround” og har måttet sige, at BEST-projektets resultater i det store hele underbygger de modeller for den globale temperaturstigning, som lå bag IPCCs store rapport fra 2007, og som har været voldsomt kritiseret.

Forskellen i de forskellige datasæt, som hidtil har været anvendt, har været meget lille, men er nu forenet i BEST-projektets samlede kurve.

I går skrev Muller i New York Times: “CALL me a converted skeptic. Three years ago I identified problems in previous climate studies that, in my mind, threw doubt on the very existence of global warming. Last year, following an intensive research effort involving a dozen scientists, I concluded that global warming was real and that the prior estimates of the rate of warming were correct. I’m now going a step further: Humans are almost entirely the cause.

My total turnaround, in such a short time, is the result of careful and objective analysis by the Berkeley Earth Surface Temperature project, which I founded with my daughter Elizabeth. Our results show that the average temperature of the earth’s land has risen by two and a half degrees Fahrenheit over the past 250 years, including an increase of one and a half degrees over the most recent 50 years. Moreover, it appears likely that essentially all of this increase results from the human emission of greenhouse gases.”¹

BEST-undersøgelsen fjernet den sidste rest af tvivl om, at de millioner målinger, som er gjort verden rundt siden midten af det 18. århundrede, tilsammen tegner et klart og entydigt billede af, at kloden bliver varmere, og at det primært skyldes menneskets stigende udledninger af klimagasser.

Hernæst mangler vi blot at se, om BEST-projektet formår at skabe den definitive enighed om klimaudfordringen, som kunne gøre, at vi kom i gang med at gøre noget ved problemerne. Eller om vi blot vil se endnu en række udenomsmanøvrer fra fornægternes side.

I denne 23:04 min. video kan man høre Richard A. Muller selv fortælle om BEST-projektet og dets konsekvenser – eller de konsekvenser han drager af det. Han kummer her med så mange levn fra skeptker-tiden, for eksempel at 90% af Al Gores statements i An Incenvenient Truth var fejlagtige, at jeg nedenfor har kopieret et indlæg på Facebook fra Michael E. Mann ind, hvor han imødegår 8 direkte fejl på klimaområdet. Mann er ophavsmand til The Hockey Stick-billedet og en af hovedmålene for klimaskeptikernes kværnen. 

Én ting er de klima-faktuelle forhold. Mindst ligeså problematisk er Mullers læsning af den politiske situation, som ligger meget på linje med den officielle amerikanske position ved klimaforhandlingerne. Der er overhovedet ikke nogen anerkendelse af den historiske situations forskellighed, at det er de industrialiserede lande, som har skabt størstedelen af klimaproblemerne, men tværtimod et meget ukonstruktivt – og meget ukldeligt – Kina-skræmmebillede. Så træerne vokser ikke ind i himlen.

Første fase af BEST-projektet blev offentliggjort i oktober, se tidligere blog-indlæg: Berkeley Earth Surface Temperature. I en senere fase vil BEST tilsvarende reevaluere verdens samlede data for havtemperaturer for hermed at nærme sig den samlede globale temperaturstigning. Men mon ikke, at vi også her vil se en konfirmation af den nu antagne globale temperaturstigning på omkring 0,7ºC siden industrialiseringens begyndelse.

indlæg oprettet af Jens Hvass

Richard A. Muller: The Conversion of a Climate-Change Skeptic, New York Times 28.07.2012.¹

Andrew C. Revkin: ‘Converted’ Skeptic: Humans Driving Recent Warming, New York Times 28.07.2012.

A two-page summary for the media is available here.

Leo Hickman: What evidence will it take to convince climate sceptics? The Guardian 30.07.2012.

Joe Romm: Bombshell: Koch-Funded Study Finds ‘Global Warming Is Real’, ‘On The High End’ And ‘Essentially All’ Due To Carbon Pollution, ThinkProgrss Blog 28.07.2012.

Jesper Løvenbalk: En klimaskeptikers bekendelser, Information 31.08.2012.

Ros Donald: The BEST is yet to come – Richard Muller on the Berkeley Earth Surface Temperature Project, whether he’s a ‘skeptic’, and BEST’s climate policy ambitions, The Carbon Brief 03.08.2012.

Micheal E. Mann via Facebook 06.08.2012 (link)

Some folks have asked me to list all 8 Richard Muller “Democracy Now” Fibs in one place so here they are:

CLAIM #1: “Al Gore’s movie, ‘An Inconvenient Truth’…essentially 90% of what he presented was exaggerated or distorted or just false.”

THE REALITY: Actually, climate scientists who have watched the movie have determined that Gore by and large got the science right. See e.g. this article: Eric Stieg: Al Gore’s movie, RealClimate 10.05.2012.

CLAIM #2: “Global warming, so far, has not been very much. In the last 50 years it’s been two-thirds of a degree Celsius, while one degree Fahrenheit, and that hasn’t been much”

THE REALITY: Its more like 1C (1.5F), and that’s more than 25% of the difference in global temperature between an Ice Age and today. Moreover, its just the tip of the iceberg. If we continue with business as usual w.r.t. fossil fuel burning, we will likely see anywhere between 3-5C (5-9F) additional warming of the globe, more than that for continents like the U.S., and nearly twice that for the Arctic.

CLAIM #3: “We need to act in a way that recognizes the problem isn’t with us.”

THE REALITY: The problem is burning of carbon and increases in the concentrations of greenhouse gases due to that. The U.S., and all industrial and developing countries contribute to this through our historical and/or continuing or emerging reliance on fossil fuels for energy. To deny any responsibility at all on the part of any major country that relies on fossil fuels (including the U.S.) seems disingenuous at best.

CLAIM #4: “The Koch Foundation made it clear to us that the reason they funded us was that we did recognize that these issues [SCIENCE THAT HAS BEEN ACCEPTED FOR TWO DECADES OR MORE] were real”

THE REALITY: The Koch brothers are the single largest funder in the world now of climate change denial and disinformation (see the discussion on this SourceWatch page: Koch Industries), as well the extensive documentation in my book “The Hockey Stick & the Climate Wars“.

It would seem that Richard Muller has served as a useful foil for the Koch Brothers, allowing them to claim they have funded a real scientist looking into the basic science, while that scientist– Muller—props himself up by using the “Berkeley” imprimatur (UC Berkeley has not in any way sanctioned this effort), appearing to accept the basic science, and goes out on the talk circuit, writing op-eds, etc. systematically downplaying the actual state of the science, dismissing key climate change impacts and denying the degree of risk that climate change actually represents. I would suspect that the Koch Brothers are quite happy with Muller right now, and I would have been very surprised had he stepped even lightly on their toes during his various interviews, which he of course has not. He has instead heaped great praise on them, as in this latest interview.


THE REALITY: As I stated the other day on Facebook: “Muller’s announcement last year that the Earth is indeed warming brought him up to date w/ where the scientific community was in the the 1980s. His announcement this week that the warming can only be explained by human influences, brings him up to date with where the science was in the mid 1990s. At this rate, Muller should be caught up to the current state of climate science within a matter of a few years!”

CLAIM #6 “[Michael Mann] has claimed that there was no Medieval warm period”

THE REALITY: Ummm, I’ve written dozens of papers about the “Medieval Warm Period” (or what scientists in my field generally now refer to as the “Medieval Climate Anomaly”, because of the considerable regional complexity of the climate anomaly during that time period).

Indeed, I devote a fair amount of space to in my book “The Hockey Stick & the Climate Wars” discussing some of the enigmatic features of this period and the work that I and other climate scientists have been focused on, for example investigations of why the tropical Pacific seems to have been in a “La Nina”-like state at that time (see e.g. our 2009 Science article: “Global Signatures and Dynamical Origins of the Little Ice Age and Medieval Climate Anomaly“) with possible implications for understanding climate change impacts on drought (see e.g. our recent PNAS article “1,500 year quantitative reconstruction of winter precipitation in the Pacific Northwest“) what the Northern Hemisphere jet stream was doing at the time (see:, and possible impacts on the behavior of tropical storms and hurricanes (see our ’09 Nature article: and the variation in global sea level (see e.g. our 2011 PNAS article: over the last millennium and beyond.

CLAIM #7 [Michael Mann has claimed] that it’s been the warmest now that it has been 1000 years.

THE REALITY: At best, a straw man as it drops the important qualifiers we have always used in describing our findings, and ignores the dozens of other confirmatory studies, including the IPCC (more on that below) and National Academy of Science (more on that later). My co-authors and I have in fact claimed, based on our work (and now the work of many others) that it is *likely* that the warmth of the most recent decades exceeds that of at least the past 1000 years at the hemispheric scale (note that we defined “likely” as a proposition for which there is roughly a 67% chance of being true).

Where this is a straw man is that this is hardly based on the work of my co-authors and me, but rather, dozens of different teams that have independently come to this conclusion over the past decade+ since our original ’98/’99 “Hockey Stick” work. Indeed, the IPCC in their 2007 (Fourth Assessment Report or ‘AR4’) came to even stronger conclusions, raising the confidence to “very likely” (90% confidence) for the past 400 years, and extending the “likely” conclusion back 1300 years (i.e. further back than the original 1000 year timeframe of our ’98/’99 work). See the AR4 “Summary for Policy Makers” on this point (): “Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years“. See also the discussion in “The Hockey Stick & the Climate Wars” about all of these issues.

CLAIM #8: “[Richard Muller] was part of that National Academy study that basically demonstrated that [Mann’s] conclusions were wrong.”

THE REALITY: A double-fibber whopper! First of all, Muller was no more “a part of that” study than I was. Despite what a reasonable listener would likely deduce from what he claimed, Muller was *not* an author of the report. There were dozens of researchers whose input was solicited for the report, which includes Muller, and which includes me.

More importantly however, the NAS actually came to the opposite of what Muller states. They reaffirmed our key findings (see e.g. Nature’s summary of the report: “Academy affirms hockey-stick graph“; the New York Times “Science Panel Backs Study on Warming Climate”; the Washington Post “Study Confirms Past Few Decades Warmest on Record”; the BBC “Backing for ‘Hockey Stick’Graph”).

The NAS report stated that our original conclusions were broadly supported by the evidence: “Th e basic conclusion of Mann et al. (1998, 1999) . . . that the late 20th century warmth in the Northern Hemisphere was unprecedented during at least the last 1,000 years . . . has subsequently been supported by an array of evidence that includes the additional large-scale surface temperature reconstructions and documentation of the spatial coherence of recent warming . . . and also the pronounced changes in a variety of local proxy indicators.” The report concluded that “based on the analyses presented in the original papers by Mann et al. and this newer supporting evidence, the committee finds it plausible that the Northern Hemisphere was warmer during the last few decades of the 20th century than during any comparable period over the preceding millennium.”

In a press release, the NAS committee asserted that there was “high confidence that [the] planet is warmest in 400 years,” “less confidence in temperature reconstructions prior to 1600,” and “little confi dence” prior to a.d. 900. The panel made it clear that their conclusions were consistent with those of MBH99. They noted that our work was “the first to include explicit statistical error bars” and reminded readers of the original MBH99 findings that “the error bars were relatively small back to about a.d . 1600, but much larger for a.d . 1000–1600,” explaining that “the lower precision during earlier times is caused primarily by the limited availability of annually resolved paleoclimate data.”

The report authors made clear in their press conference that they backed the key conclusions of our original work. Chair Gerald North stated that “We roughly agree with the substance of their findings.” Andrew Revkin of the New York Times, noting that we had indeed emphasized the importance of uncertainties and caveats in our original millennial hockey stick analysis (MBH99), asked the panel at the press conference who, if anyone, may have been responsible for any overstating of our conclusions. North stated that “the community probably took the results to be more definitive than Mann and colleagues intended.”

You can find extensive discussion of the Academy report and the discredited, dueling “Wegman Report” solicited by fossil fuel lap dog Joe Barton (R-TX) in my chapter “A Tale of Two Reports” and all the surrounding political theater, in “The Hockey Stick & the Climate Wars“.