Friday, May 30, 2008

A blip in the temperature record

An article in Nature concludes that a previously unexplained dip in global sea surface temperatures (SSTs) in the 1945 is actually due to a change in the way measurements were taken at the end of WWII. You can see the dip in the IPCC's temperature plots - look at the global ocean's observed line.

Until we developed global satellite coverage in the 1980s, SST was measured by ships and the methods - buckets brought on deck, buckets dropped in the ocean, etc. - changed over time. The people who put together the global SST datasets expend a ton of effort analysing and accounting for the measurement bias caused by the different methods. As RealClimate explains, this discovery did not come out of the blue, to use some ocean lingo. It is builds upon the ongoing analysis of bias in different measurement methods.

The article and the accompanying News and Views summary in Nature explains the likely implications for the global temperature record. The 0.3 C blip due to the 1945 switch in methodology likely means the immediate post-war SSTs were underestimated. In that case, it would reduce or eliminate the "observed" cooling in the late 40s and the 50s, a period that has flummoxed climate modelers, not alter the entire post-war temperature record. As the News and Views opens: "An unseen measurement bias has been identified in global records of sea surface temperature. The discrepancy will need correction, but will not affect conclusions about an overall warming trend."

Nonetheless, some have jumped on the paper as possible evidence of a problem with the basic conclusions of the IPCC. It is not. Once again, what we have is a case of impatience, of not looking (or reading the whole paper), before leaping.


The time to discuss a carbon tax

It is “Bike to Work week" here in Vancouver. The timing, you might argue, is perfect, and not only because the infamous Pacific Northwest rains have petered out for the summer. Evidence is mounting that we are approaching the elastic part of the gas price equation.

The increase in gas and oil prices – and especially the threat of a continued increase – is beginning to impact North American driving habits. Americans drove 11 billion fewer miles this March, than the previous March, a drop of 4.3%. Trucking companies are telling drivers to slow down and to reduce idling. Auto dealers are selling fewer SUVs and trucks than cars for the first time in years. last March. SUV and truck sales are plummeting. Public transit use is increasing. And, yes, there is anecdotal evidence that more North Americans are cycling to work, though I attribute the large number of cyclists trudging up the hill to the UBC campus this week to the sunny weather and the promise of a free cup of coffee, not to gas prices (nothing motivates people in the Pacific Northwest more than a sunny day or a coffee).

These are the sort of behavioural shifts that may be encouraged by a tax on the carbon content of fuels. That does not mean that anyone should celebrate the current rise in gas prices. The problem right now is that the proceeds from the gas price increase is going almost entirely to the oil companies (see Salon's Andrew Leonard for a terrific breakdown of the cost of gasoline). This is essentially subsidizing exploration in regions previously deemed unprofitable, in effect opposing the very initiatives necessary to reduce our reliance on oil. If, on the other hand, gas prices had increased because of taxation, the proceeds could go towards public transit, increasing fleet fuel efficiency and alternative fuel development, initiatives that could reduce our reliance on oil and relieve the burden on the public.

Adding a tax based on carbon content of fuels, even a revenue neutral one like that suggested by Canada's Liberal Party, is politically challenging at a time when oil prices are already high. But if we do not add a tax, then the oil companies remain the sole beneficiaries. That's just one reason the time is right to seriously consider a federal tax on carbon as the key part of a carbon pricing policy.

The Liberals floated a trial balloon, presumably to test public opinion and the response of the other parties. The discussion since then has been dominated by politics. There are serious arguments one could make against a carbon tax: you will not find them in the blatantly manipulative Conservative response or, for that matter, the surprisingly negative NDP response. The signs suggest the public is ready to accept a carbon pricing policy. Is it naive to hope the choice - a tax, a cap-and-trade system, or a combination of the two - is based on the policy itself, not the politics?


Tuesday, May 13, 2008

King Corn and the food crisis

Last weekend, I was asked to answer a few questions after a local screening the film "King Corn", an offbeat documentary by a couple young college grads who decided to move to Iowa and try growing the crop that fuels us all. The audience questions centered around the usual public fears about food. Is all corn GMO? What animals can eat corn? What else are they fed? Where can I learn more? And, my favourite, is the "glucose-frutcose" listed on my bottle of Arizona Iced Tea made from corn?

I'm not an expert on all those subjects - and I admitted as much at the screening. I can say that the answer to that last one - yes - got me thinking more about the uses of our crops and the causes of the world food crisis.

Frankly, any ingredient that you do not recognize on the label of a processed food or beverage is probably made from corn. Xathan gum? A fermented sugar made from corn. Lecithin? Made from corn. Vanilla extract? Vanilla and corn syrup. Malt extract? Often made from corn, not barley. Dextrin? As Michael Pollan would say, corn, corn, corn.

Corn is so ubiquitous in our food today, that it is natural to assume that food is the reason we grow so much corn. But all those food additives and sugars made from corn, including the bane of nutritionists and foodies, high-fructose corn syrup (I highly recommend the scene in King Corn where the protagonists try to make some in their kitchen), still only make up a small fraction of the corn crop. The US don't produce corn to make high-fructose corn syrup, it produces high-fructose corn syrup because it has developed an agricultural system that profits on producing large volumes of corn anyway. The majority of that corn, until very recently, was bring to animals, largely beef cattle.

The graph to the left shows the end use of US corn over the past six years (all data that follows is from the Foreign Agriculture Service and the Economic Research Service of the USDA). The big pink block in the middle is domestic feed use (~60%, down to 47% last year). The top category is exports, most of which is also used as feed (19%). The dreaded high-fructose corn syrup has been around 7% (5% last year) of the corn crop, glucose / dextrose around 2-3%, beverage alcohol (yep, there's corn in that Bud Light) around 1-2%. Cereals and other foods? 2%.

The one area of growth (in blue) is fuel alcohol, or ethanol. Last year, 24% of all US corn production (29% of non-export corn) was used for ethanol. The percent breakdown of corn use changed the last few years as a result of the ethanol surge. But the other uses of corn, in terms of raw numbers did not. Exports and feed use were relatively flat (an assumption made in our paper on the subject). The US simply grew more corn to produce ethanol. As many have been arguing, that is why US production of corn-based ethanol has not played a role in the global food crisis. No harm, no foul, right?

Tempting, but there are two holes in that argument.

First, the extra corn for ethanol has to be planted on productive croplands, lands with the right soils, and most of that land is being used. In 2007, soybean planting - the other major feed crop grown in the midwest US - went down 16% in the US to make space for more corn. Soybean exports and use remained the same, but the ending stocks were down 72%. In other words, we've been cleaning out the cupboards.

Soy planting is back up to 2006 levels this year, as prices rose and farmer rotate those fields full of corn back to soy, as is common practice. If the US to keep up ethanol production, soy planting will probably drop again the following year, or corn exports will go down. In other words, if corn ethanol production is to continue or increase, the US is most likely going to have to i) export less corn, ii) export less soybean, or iii) produce less domestic feed.

Complicated business - and potentially very profitable business. If you are a speculative investor with a fast computer, there's a lot of money to be made betting on crop production. The world relies on a very small number of staple crops for food and feed: corn, soybeans, wheat, rice, and other regional crops like cassava. The planted area, production and price of one can affects the others. The ethanol surge in the US paved the way for more speculative investment in commodities, which has helped drive up prices.

Second, the US is the world's largest producer of corn and soybeans. The demand for both has been rising for years because of rising meat consumption in Asia.. The US produced 43% of world’s corn in 2007/2008 (right). The US is also responsible for two-thirds of all the global corn exports. If you need to buy some corn, there are few other places to shop. Last year, the amount of corn used for ethanol in the US in 2007/2008 is greater than the domestic corn production of every other country in the world, save China. That's taking a lot of potential grain off the market. Now, yes, exports remained steady last year. But to meet the growing demand - feed consumption in China alone is rising a few percent a year - exports should be growing. The signs point to, at best, exports remaining constant, or at worst, exports decreasing.

There are a lot of causes of the current food price crisis - I recommend the FAO's website for information. Many have called it a perfect storm of oil prices, ethanol production, rising meat consumption, drought, price speculation, rising population. The corn-based ethanol surge in the US is not the sole cause, by any means, but it has played a role.

The global food system may have been a dam that was ready to break. The growing population and growing demand for animal feed had filled the reservoir up to capacity. The US ethanol policy helped crack some holes in the concrete.


Sunday, May 11, 2008

Shifting diets vs. eating local

I finally had the chance to read this terrific paper by Christopher Weber and Scott Matthews of Carnegie Mellon that compares greenhouse gas emissions from the production different types of food and the delivery of that food to your plate. As was reported by some news agencies and blogs, Weber and Matthews conclude that transportation represents only 11% - on average, it depends on the food – of the total life-cycle GHG emissions of U.S. food (there’s little reason to expect a dramatically different result in Canada).

The take home message is shifting your diet will do far more to reduce greenhouse gas emissions than buying local. From the paper:


The authors did some simple calculations to demonstrate this point:

To put these figures into perspective, driving a 25 mi/gal (9.4 L/100 km) automobile 12 000 miles/yr (19 000 km/yr) produces around 4.4 t CO2/ yr. Expressed in this manner, a totally “localized” diet reduces GHG emissions per household equivalent to 1000 miles/yr
(1600 km/yr) driven, while shifting just one day per week’s calories from red meat and dairy to chicken/fish/eggs or a vegetable-based diet reduces GHG emissions equivalent to 760 miles/yr (1230 km/yr) or 1160 miles/yr (1860 km/yr), respectively. Shifting totally away from red meat and dairy toward chicken/fish/eggs or a vegetable-based diet reduces GHG emissions equivalent to 5340 mi/yr (8590 km/yr) or 8100 mi/yr (13 000 km/yr), respectively.

It is important to note that macro-scale GHG “accounting” studies always come with a number of caveats. The calculations or model requires a number of simplifying assumptions and often some more complicated factors are often excluded. The two central limitations to this particular study appear to be the simple treatment of direct GHG emissions from animal and crop production (i.e. N2O from manure, fertilizer and the animals themselves) and the exclusion of land use impacts and the “land use cascade” (i.e. carbon released from directly or indirectly transforming land for crop or animal production). Improving those components of their mode should increase the share of GHG emissions from food production and the relative GHG emissions from red meat production. In other words, that provides even more support for the conclusion that eating less beef is one of the best ways to reduce personal greenhouse gas emissions.


Saturday, May 10, 2008

The globe is warming, except in the headlines

"Global cooling theories put scientists on guard"

Reuters publishes a more or less reasonable article about the controversy surrounding the Keenlyside et al decadal modelling paper. No problem with that.

But the headline? Abominable.

There is no reputable theory - or theories - that the planet has been cooling or will be cooling [update: see RealClimate's deconstruction of the IPCC model simulations]. Even the paper in question does not assert as much. The paper is about a possible leveling off of temperatures over the next decade due to internal or background climate variability. The paper confirms the widespread scientific consensus about global warming.

Headlines like this only continue this ongoing, ridiculous meme about that global warming has stopped, a meme based on confusion between weather and climate, impatience for news, and the misuse and abuse of statistics, rather than any serious evidence. The above figure from the UK Hadley Centre (thanks to Joe Romm for the reminder of this one) ranks global temperatures over the past 157 years. Your top ten, in order? 1998, 2005, 2003, 2002, 2004, 2006, 2007, 2001, 1997, 1995.


Will Canada vote for a carbon tax?

The news came this week, via one of those not-so-subtly leaked trial balloons, that Canada's Liberal Party may advocate a revenue-neutral carbon tax. It may seem like political suicide for embattled Liberal leader Stephane Dion to even casually mention a tax on fuels at a time when gas prices are soaring. The Canadian political pundits I've heard have used the example of the way northern BC communities and opposition parties responded to the BC government's upcoming carbon tax, a tax that will add only 2 to 7 cents per litre at the pump, less than the price of gas increased in the past week at the Esso station down the street from my house!

That's why we need fewer political pundits.

Is there a better time to redirect federal tax code to stress fuels, rather than income? The signals are all pointing in that direction. Cars are outselling trucks and SUVs for the first time in years. Goldman Sachs reported this week that oil could reach $150 to $200 a barrel. Public transit usage is on the rise. A carbon tax on transportation and heating fuels would only further nudge our economy towards higher energy efficiency and lower per capita greenhouse gas emissions. Most importantly, even if 100% revenue neutral the tax will allow the government the political room to direct revenues to programs to further invest in energy efficiency, renewable energy and new technologies.

As for the politics: evidence from the US primaries, where Hillary Clinton's obvious pandering over a gas tax holiday appears to have sunk what was left of her presidential campaign, that people do appreciate honest on the complex issues of today. Dion is in the strange position of being seen by Canadians as "weak, uninspiring and unintelligible" but still more likable than PM Stephen Harper. Voters across the spectrum might just respect Dion more for making seemingly risky and groundbreaking political move of pushing for a carbon tax.

But, hey, I'm no pundit.


Monday, May 05, 2008

More global cooling lunacy

I recently cautioned patience in the reporting of each month's climate data or every new study, as if they were proof or disproof of climate change. Sadly, we didn't have to wait long for an example of the problem. The media bungling and flagrant online abuse of a study on decadal climate prediction published in last week's Nature is a textbook case of pouncing on - and twisting - every new scrap of data related to climate change. This reporting and blogging train wreck is so textbook that I already plan to use it as a case study in my climate class next year (which limits what I can write here...)

The study by Keenlyside et al. tested whether a simplified climate model could make decadal (short-term by climate standards) forecasts. At issue is realistically simulating the many internal variations in the climate system - oscillations like the Atlantic Multi-decadal Oscillation (why people claim Atlantic hurricane activity 'naturally' varies over time) and the Pacific Decadal Oscillation - that make some decades warmer or cooler than others. The authors developed a modeling approach that exhibited some 'skill', to use the meteorologists term, in hindcasting previous ten-year periods. All in all, it is a reasonable effort; I'll spare a detailed analysis of the limits of their methodology here (but see William Connolley for a critical reading).

At the end of the manuscript, it was used to forecast temperatures over the next ten years (figure). The model forecasts a leveling off in the global temperature rise over the next decade (green / black lines), due to these internal variations in the climate system, followed by a continuation of the temperature rise.

Nowhere does it say climate change is over. This is a paper about whether models can make decadal predictions. The results confirm what we know, that internal variability is superimposed on any long-term warming trend. The global warming projections you see often look smooth or monotonic because they are averages of many individual model simulations or "realizations" of the climate (averaging them together reduces the "noise" in the data). So the paper doesn't contradict the existing consensus on a long-term rise in temperatures.

Their model forecasts the possibility that temperatures will not increase in some decades like the next decade - which is NOT the same as saying that temperatures will decrease - but will increase more in other decades.
Look at the figure: the next decade is WARMER than any of the previous decades. Nothing about the end of global warming. Yet the story that hit the press was "scientists predict global warming may stop" (Telegraph).

As with the Darfur lake fiasco last year, the authors of the press release may shoulder some of the blame. The opening "Global warming may take a short break" played up an angle sure to draw interest from the media. That does not absolve the authors of the global warming may stop silliness, both in the traditional media and that grand echo-chamber we call the blogosphere. It is not clear many of them read the press release, let alone the paper, (Pielke's flubbing the numbers seems proof of that) as the release very clearly states that the goal of the study was to look at decadal variability, and included this important quote from the authors:

"Just to make things clear: we are not stating that anthropogenic climate change won’t be as bad as previously thought”, explains Prof. Mojib Latif from IFM-GEOMAR. “What we are saying is that on top of the warming trend there is a long-periodic oscillation that will probably lead to a to a lower temperature increase than we would expect from the current trend during the next years”, adds Latif. “That is like driving from the coast to a mountainous area and crossing some hills and valleys before you reach the top”, explains Dr. Johann Jungclaus from the MPI for Meteorology. “In some years trends of both phenomena, the anthropogenic climate change and the natural decadal variation will add leading to a much stronger temperature rise."

The good news is that there are people like Andy Revkin of the NY Times (Dot Earth) out there, who tends to avoid the cheap stunt headlines and stories. Revkin's NY Times piece was like a pre-empitive strike against all the silliness to come.

[Update: For more, try this post from the prolific Joe Romm.]


Friday, May 02, 2008

China's CO2 emissions

USA Today reports that a trio of new studies all conclude that China has become the number one industrial emitter of CO2, ahead of the United States.

The article - and all the other news coverage I've seen - fails to mention the salient point that there are, at last count, 1.323 billion people in China and 304 million people in the US. Per capita, US CO2 emissions remain four times that of China.

Even with the new results, if you ranked countries by their per capita greenhouse gas emissions emissions, China would rank somewhere around 75th, close to the French Guiana and American Samoa. And a substantial fraction of China's emissions are generated while producing stuff for North Americans.

China's greenhouse gas emissions are a serious matter for the climate and for international climate policy. But can we stop pretending that the average person in China is living like the average North American?