Saturday, December 20, 2008

Real Climate: 2008 temperature summaries and spin

Excerpts of article 2008 temperature summaries and spin in Real Climate,

The great thing about complex data is that one can basically come up with any number of headlines describing it - all of which can be literally true - but that give very different impressions. Thus we are sure that you will soon read that 2008 was warmer than any year in the 20th Century (with the exception of 1998), that is was the coolest year this century (starting from 2001), and that 7 or 8 of the 9 warmest years have occurred since 2000. There will undoubtedly also be a number of claims made that aren't true; 2008 is not the coolest year this decade (that was 2000), global warming hasn't 'stopped', CO2 continues to be a greenhouse gas, and such variability is indeed predicted by climate models. Today's post is therefore dedicated to cutting through the hype and looking at the bigger picture.

As is usual, today marks the release of the 'meteorological year' averages for the surface temperature records (GISTEMP, HadCRU, NCDC). This time period runs from December last year through to the end of November this year and is so-called because of the fact that it is easier to dice into seasons than the calendar year. That is, the met year consists of the average of the DJF (winter), MAM (spring), JJA (summer) and SON (autumn) periods (using the standard shorthand for the month names). This makes a little more sense than including the JF from one winter and the D from another as you do in the calendar year calculation. But since the correlation between the D-N and J-D averages is very high (r=0.997), it makes little practical difference. Annual numbers are a little more useful than monthly anomalies for determining long term trends, but are still quite noisy.

The bottom line: In the GISTEMP, HadCRU and NCDC analyses D-N 2008 were at 0.43, 0.42 and 0.47ºC above the 1951-1980 baseline (respectively). In GISTEMP both October and November came in quite warm (0.58ºC), the former edging up slightly on last month's estimate as more data came in. This puts 2008 at #9 (or #8) in the yearly rankings, but given the uncertainty in the estimates, the real ranking could be anywhere between #6 or #15. More robustly, the most recent 5-year averages are all significantly higher than any in the last century. The last decade is by far the warmest decade globally in the record. These big picture conclusions are the same if you look at any of the data sets, though the actual numbers are slightly different (relating principally to the data extrapolation - particularly in the Arctic).

So what to make of the latest year's data? First off, we expect that there will be oscillations in the global mean temperature. No climate model has ever shown a year-on-year increase in temperatures because of the currently expected amount of global warming. A big factor in those oscillations is ENSO - whether there is a a warm El Niño event, or a cool La Niña event makes an appreciable difference in the global mean anomalies - about 0.1 to 0.2ºC for significant events. There was a significant La Niña at the beginning of this year (and that is fully included in the D-N annual mean), and that undoubtedly played a role in this year's relative coolness. It's worth pointing out that 2000 also had a similarly sized La Niña but was notably cooler than this last year.

While ENSO is one factor in the annual variability, it is not the only one. There are both other sources of internal variability and external forcings. The other internal variations can be a little difficult to characterise (it isn't as simple as just a super-position of all the climate acronyms you ever heard of NAO+SAM+PDO+AMO+MJO etc.), but the external (natural) forcings are a little easier. The two main ones are volcanic variability and solar forcing. There have been no climatically significant volcanoes since 1991, and so that is not a factor. However, we are at a solar minimum. The impacts of the solar cycle on the surface temperature record are somewhat disputed, but it might be as large as 0.1ºC from solar min to solar max, with a lag of a year or two. Thus for 2008, one might expect a deviation below trend (the difference between mean solar and solar min, and expecting the impact to not yet be fully felt) of up to 0.05ºC. Not a very big signal, and not one that would shift the rankings significantly.

There were a number of rather overheated claims earlier this year that 'all the global warming had been erased' by the La Niña-related anomaly. This was always ridiculous, and now that most of that anomaly has passed, we aren't holding our breath waiting for the 'global warming is now back' headlines from the same sources.

Taking a longer perspective, the 30 year mean trends aren't greatly affected by a single year (GISTEMP: 1978-2007 0.17+/-0.04ºC/dec; 1979-2008 0.16+/-0.04 - OLS trends, annual data, 95% CI, no correction for auto-correlation; identical for HadCRU); they are still solidly upwards. The match of the Hansen et al 1988 scenario B projections are similarly little affected (GISTEMP 1984-2008 0.19+/-0.05 (LO-index) 0.22+/-0.07 (Met-station index); HansenB 1984-2008 0.25+/-0.05 ºC/dec) - the projections run slightly warmer as one would expect given the slightly greater (~10%) forcing in the projection then occurred in reality. This year's data then don't really change our expectations much.


A Chance for Consensus on Iraq. By John McCain, Joe Lieberman and Lindsey Graham

A Chance for Consensus on Iraq. By John McCain, Joe Lieberman and Lindsey Graham
Washington Post, Dec 19, 2008.

After our visit to Iraq this month, it is clear that what was once unthinkable there is now taking place: A stable, safe and free Iraq is emerging. Violence has fallen to the lowest level since the first months of the war. The Sunni Arabs who once formed the core of the insurgency are today among our most steadfast allies in the fight against al-Qaeda. A status-of-forces agreement between Iraq and America will take effect next month, providing for the withdrawal of U.S. troops and a commensurate increase in Iraqi self-defense. And Iraqi politics is increasingly taking on the messy but exhilarating quality of a functioning democracy. While uncertainty and risk remain high, and the gains made are not irreversible, the situation in Iraq has improved dramatically since the dark days before the surge.

Now it's time for the unthinkable to take place in Washington. For the past several years, Iraq has divided and polarized our parties, our policymakers and our people. The debate over the war has often been disfigured by politics and partisanship, precluding the national consensus so important to American security in a dangerous world. President-elect Barack Obama has the opportunity to end this destructive dynamic and rebuild a bipartisan consensus on American foreign policy, including the way forward in Iraq. In naming talented, principled and pragmatic leaders to his national security cabinet, the president-elect has already demonstrated that he wants to set aside foreign policy politics as usual. Now the very capable leadership team of Defense Secretary Bob Gates, Secretary of State-designate Hillary Clinton and Gen. Jim Jones, the incoming national security adviser, can apply their bipartisan credentials to help the president-elect forge an Iraq policy that will garner the support of Democrats and Republicans alike.

No longer does Congress need to be locked in partisan trench warfare over withdrawal dates and funding cutoffs. Our shared, central task now is to work together to support a responsible redeployment from Iraq, based on the new and improved realities on the ground.

To achieve this, the president-elect, his national security team and all of us in Congress should seek the counsel of Gen. David Petraeus, the head of U.S. Central Command, and Gen. Ray Odierno, commander of coalition forces in Iraq. Gen. Odierno was the operational architect of the surge in 2007, when he served as deputy to Gen. Petraeus, as well as of the tribal engagement strategy that persuaded Sunnis to abandon the insurgency and join our side. Gen. Odierno -- as the current commander on the ground -- is the person whose judgment should matter most in determining how fast and how deep a drawdown can be ordered responsibly.

John McCain (R-Ariz.), Joe Lieberman (Independent Democrat-Conn.) and Lindsey Graham (R-S.C.) are members of the U.S. Senate.

WaPo Editorial On W. Mark Felt

W. Mark Felt
In an ambiguous career, an anonymous source did his country a great service.

OLD MEN forget," says the Shakespearean warrior-king on the day of battle, yet there are those who will "remember with advantages" what feats they did in times of strife, when great issues were decided. W. Mark Felt Sr., who died Thursday at the age of 95, never really availed himself of that old man's privilege. He played a key role in bringing down an administration that badly abused its powers, but he did it in secret, and he kept that secret almost to the grave. By the time he revealed his identity -- just 3 1/2 years ago -- the anonymous source known as "Deep Throat" had been struck down by common calamities of age -- stroke and dementia. So much for remembering with advantage.

But, then, Mr. Felt was never all that certain whether he would be regarded as a hero or a turncoat. As a high FBI official with intimate knowledge of what was going on in the Nixon administration during its frantic efforts to cover up Watergate and other misdeeds, he helped Bob Woodward of The Post immeasurably. He served as a valuable anonymous source while the team of Woodward and Carl Bernstein worked the biggest scandal story in ages. Mr. Felt could tell himself -- and certainly many would have told him -- that he was doing the country an invaluable service, that he had no choice but to reveal the secret information entrusted to him.

But Mark Felt was also a creature of the FBI -- J. Edgar Hoover's FBI -- and he knew that what he was doing would be seen by many of his colleagues as a betrayal. Given what we know, and continue to learn, about Mr.

Hoover's abuses of power, the loyalty that Mr. Felt displayed to him and to his legacy only adds to the ambiguity of his career. In fact, it led to his conviction on charges of authorizing illegal break-ins at the premises of antiwar radicals and their families -- for which Mr. Felt received a pardon from Ronald Reagan.

Mark Felt inhabited a world in which good and talented and diligent people such as himself could feel it was a justifiable act to spy on someone of the stature of Martin Luther King Jr. It is a world in which many things, good and bad, come under the broad rubric of "security." Few who operate in it emerge as pristine heroes, as we continue to be reminded. But Shakespeare notwithstanding, there's not much likelihood by this time that the good Mark Felt did will be interred with his bones.