Open Mind

Cyclical? Probably not.

December 31, 2009 · 12 Comments

It’s way too easy to look at data and think you see cycles. After all, if it went down, then up, then down, then up — it must be cyclic, right? The amount of analysis that goes into such conclusions is often limited to “Looks pretty cyclical to me.” Such “analysis” is tantamount to seeing a rock formation on Mars that looks vaguely like a face, and concluding that aliens constructed it millions of years ago as a message to future humanity.

The tendency to see cycles where there are none spurs people to extrapolate their imaginary “cycles” into the future, leading to some expectation about economic recovery, or a world series victory for the Mets, or what is an all too common, imminent global cooling. It also enables those in denial to explain away the global warming we have observed with a wave of the hand, dismissing it as “natural cycles.”

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Exogenous Factors

December 31, 2009 · 19 Comments

Apparently Lucia thinks that my “estimation of uncertainty intervals without treating the effect of volcanic eruptions like Pinatubo as exogeneous is very misleading.” I’ve come to expect such foolishness from her; whenever she approaches the trend in temperature data, she reeks of desperation.

But if we do model some of the exogenous factors, we might get smaller uncertainties in our trend estimates. Yay! Let’s give that a try.

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Open Thread #17

December 24, 2009 · 146 Comments

Merry Christmas.

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Cyclical? Not.

December 22, 2009 · 36 Comments

Over at RealClimate, a commenter by the monicker of manacker insists that global temperature follows a cyclic pattern. His “analysis” to establish this consists of saying, “Looks pretty cyclical to me.”

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Message from Santer

December 17, 2009 · 124 Comments

Eli Rabett has posted the text of a statement made by Ben Santer at the recent AGU meeting (reproduced with Santer’s permission). I’ll assume that Santer wants his message made more public and that he won’t object to my also reproducing it here.

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How Long?

December 15, 2009 · 180 Comments

Time and time again, denialists try to suggest that the last 10 years, or 9 years, or 8 years, or 7 years, or 6 years, or three and a half days of temperature data establish that the earth is cooling, in contradiction to mainstream climate science. Time and time again, they’re refuted — shown to be either utterly foolish or downright dishonest or both. Logic seems to have no effect on them.

The simple fact is that short time spans don’t give enough data to establish what the trend is, they just exhibit the behavior of the noise. Of course that raises an interesting question: how long a time span do we need to establish a trend in global temperature data? It’s sometimes stated that the required time is 30 years, because that’s the time span used most often to distinguish climate from weather. Although that’s a useful guide, it’s not strictly correct. The time required to establish a trend in data depends on many things, including how big the trend is (the size of the signal) and how big, and what type, the noise is. Let’s look at GISS data for global temperature and test how much data we need to establish the most recent trend.

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The better angels of our nature

December 8, 2009 · 24 Comments

Fifty-six newspapers worldwide are running, on the front page, this editorial from the Guardian:


Today 56 newspapers in 45 countries take the unprecedented step of speaking with one voice through a common editorial. We do so because humanity faces a profound emergency.

Unless we combine to take decisive action, climate change will ravage our planet, and with it our prosperity and security. The dangers have been becoming apparent for a generation. Now the facts have started to speak: 11 of the past 14 years have been the warmest on record, the Arctic ice-cap is melting and last year’s inflamed oil and food prices provide a foretaste of future havoc. In scientific journals the question is no longer whether humans are to blame, but how little time we have got left to limit the damage. Yet so far the world’s response has been feeble and half-hearted.

Climate change has been caused over centuries, has consequences that will endure for all time and our prospects of taming it will be determined in the next 14 days. We call on the representatives of the 192 countries gathered in Copenhagen not to hesitate, not to fall into dispute, not to blame each other but to seize opportunity from the greatest modern failure of politics. This should not be a fight between the rich world and the poor world, or between east and west. Climate change affects everyone, and must be solved by everyone.

The science is complex but the facts are clear. The world needs to take steps to limit temperature rises to 2C, an aim that will require global emissions to peak and begin falling within the next 5-10 years. A bigger rise of 3-4C — the smallest increase we can prudently expect to follow inaction — would parch continents, turning farmland into desert. Half of all species could become extinct, untold millions of people would be displaced, whole nations drowned by the sea. The controversy over emails by British researchers that suggest they tried to suppress inconvenient data has muddied the waters but failed to dent the mass of evidence on which these predictions are based.

Few believe that Copenhagen can any longer produce a fully polished treaty; real progress towards one could only begin with the arrival of President Obama in the White House and the reversal of years of US obstructionism. Even now the world finds itself at the mercy of American domestic politics, for the president cannot fully commit to the action required until the US Congress has done so.

But the politicians in Copenhagen can and must agree the essential elements of a fair and effective deal and, crucially, a firm timetable for turning it into a treaty. Next June’s UN climate meeting in Bonn should be their deadline. As one negotiator put it: “We can go into extra time but we can’t afford a replay.”

At the deal’s heart must be a settlement between the rich world and the developing world covering how the burden of fighting climate change will be divided — and how we will share a newly precious resource: the trillion or so tonnes of carbon that we can emit before the mercury rises to dangerous levels.

Rich nations like to point to the arithmetic truth that there can be no solution until developing giants such as China take more radical steps than they have so far. But the rich world is responsible for most of the accumulated carbon in the atmosphere – three-quarters of all carbon dioxide emitted since 1850. It must now take a lead, and every developed country must commit to deep cuts which will reduce their emissions within a decade to very substantially less than their 1990 level.

Developing countries can point out they did not cause the bulk of the problem, and also that the poorest regions of the world will be hardest hit. But they will increasingly contribute to warming, and must thus pledge meaningful and quantifiable action of their own. Though both fell short of what some had hoped for, the recent commitments to emissions targets by the world’s biggest polluters, the United States and China, were important steps in the right direction.

Social justice demands that the industrialised world digs deep into its pockets and pledges cash to help poorer countries adapt to climate change, and clean technologies to enable them to grow economically without growing their emissions. The architecture of a future treaty must also be pinned down – with rigorous multilateral monitoring, fair rewards for protecting forests, and the credible assessment of “exported emissions” so that the burden can eventually be more equitably shared between those who produce polluting products and those who consume them. And fairness requires that the burden placed on individual developed countries should take into account their ability to bear it; for instance newer EU members, often much poorer than “old Europe”, must not suffer more than their richer partners.

The transformation will be costly, but many times less than the bill for bailing out global finance — and far less costly than the consequences of doing nothing.

Many of us, particularly in the developed world, will have to change our lifestyles. The era of flights that cost less than the taxi ride to the airport is drawing to a close. We will have to shop, eat and travel more intelligently. We will have to pay more for our energy, and use less of it.

But the shift to a low-carbon society holds out the prospect of more opportunity than sacrifice. Already some countries have recognized that embracing the transformation can bring growth, jobs and better quality lives. The flow of capital tells its own story: last year for the first time more was invested in renewable forms of energy than producing electricity from fossil fuels.

Kicking our carbon habit within a few short decades will require a feat of engineering and innovation to match anything in our history. But whereas putting a man on the moon or splitting the atom were born of conflict and competition, the coming carbon race must be driven by a collaborative effort to achieve collective salvation.

Overcoming climate change will take a triumph of optimism over pessimism, of vision over short-sightedness, of what Abraham Lincoln called “the better angels of our nature”.

It is in that spirit that 56 newspapers from around the world have united behind this editorial. If we, with such different national and political perspectives, can agree on what must be done then surely our leaders can too.

The politicians in Copenhagen have the power to shape history’s judgment on this generation: one that saw a challenge and rose to it, or one so stupid that we saw calamity coming but did nothing to avert it. We implore them to make the right choice.

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Riddle me this …

December 7, 2009 · 198 Comments

Those who are in denial of global warming insist that the last decade of global temperature contradicts what was expected by mainstream climate scientists.

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Hack

November 22, 2009 · 311 Comments

Most of you are probably already aware that recently someone managed to hack into the computer system at CRU (the Climate Research Unit in Great Britain). They stole over 60 megabytes of personal emails, which was posted online.

The denialosphere has trumpeted the contents as proof of the fraudulent behavior of climate scientists, especially Phil Jones at CRU. But what’s most remarkable is that even the bits pointed to as a “smoking gun” really don’t support that idea. There are certainly phrases which seem incriminating when taken out of context — but when put into context are nothing of the kind.

Continuing to suggest that climate scientists generally, and Phil Jones specifically, are engaged in a conspiracy to deceive the world about global warming, when there turns out to be no real evidence of it in 10 years of personal communications (only words that can be twisted when taken out of context), demonstrates the idiocy of those who stand by that suggestion. If anything, the messages prove that there is not any conspiracy, and the scientists at CRU did not fudge data or engage in deceptive practices to push their “agenda.”

Certainly the emails contain some unkind words about certain people. I’ve said unkind things about some of them myself (here on this blog for all to see). In my opinion, the unkind words were earned by the loathesome recipients.

Perhaps the most enlightening revelation to come out of this sordid episode is how Gavin Schmidt (at RealClimate) has addressed the issue head-on but avoided any temptation to indulge in mud-slinging, even in the midst of this despicable invasion of privacy, unjustified by any of the contents of the messages. His conduct is exemplary, and illustrates a character and self-control that I can only envy. My respect for him knows no bounds.

My disrespect for the theives in likewise unbounded. They stole private communications, found nothing damning, but proved how willing — nay, eager — they are to distort things to make it seem as though they did. It’s every bit as immature and vindictive as stealing your sister’s diary and posting it on the internet. If she’d confessed to murder, there might be a reason to bring that to light, but when the worst you can find is that she said “I hate that bitch,” you have no business making her private thoughts public.

But that’s the level of the denialists. We’ve known for some time that their scientific arguments are completely bankrupt; now we know that they’re morally bankrupt too.

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Born-Again Bayesian

October 29, 2009 · 43 Comments

I’m finally getting to the point where I can do my own typing (this is my hand, not Mrs. Tamino’s), but I’ve fallen far enough behind that I have catching up to do in lots of areas. Still, I thought I should resume blogging with a thank-you to readers.

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