Here's the link to the story The full report (pdf file) can be found here.

"The U.S. could lose $1.4 billion in annual corn revenue, the report says." Of course, global warming is the problem. The problem is, the report is pure nonsense. It's produced by a political activist organization, and its author isn't qualified to have an opinion on the matter. The most telling passage of the story is this:

"Corn likes it cool, but global warming is raising temperatures across the nation," said report author Timothy Telleen-Lawton in a news release. "Hotter fields will mean lower yields for corn, and eventually, the rest of agriculture."

This is pure nonsense. There are a number of reasons (including that they must be ignoring the effects on regions further north, and the possibility of shifting to corn types that are better suited to the new temp ranges) but the part I'd like to dwell on now is the very nature of corn itself. Corn is a member of a relatively recent genetic mutation in photosynthesis using organisms. Photosynthesis has been taking place on the Earth for roughty 3.5 billion years, but about 34 million years ago certain plants starting using a new process. To put it simply, prior to this all photosynthesis was C3 (carbon 3) photosynthesis. Corn (and sugar, sorghum, and switch grass among others) are members of a more limited range of plants that make use of the C4 (carbon 4) process of photosynthesis. There are a lot of interesting implications of this, but we'll concentrate on the most pertinent for this topic. C4 photosynthesis operates more efficiently at higher temperatures than C3 photosynthesis, and C4 also prefers higher levels of CO2 than its C3 rivals. The upshot? Corn, and other C4 plants, actually benefit in all sorts of ways from increased human emissions and raised temperatures, not least in gaining a major competitive advantage over non C4 plants (which basically includes everything except varieties of grass).

Let's take a detailed look at the report now. Given my own time constraints, I don't have time to break down each and every piece of misdirection and/or misunderstanding, so we'll just take the author's first footnoted reference as a case in point.

Climate changes since 1981 have already cost corn growers worldwide about $1.2 billion per year.

Let's look now to the "evidence" for this statement. The author cites the article "Global Scale Climate - Crop Yield Relationships and the Impacts of Recent Warming" by DB Lobell and CB Field. (Published in ENVIRONMENTAL RESEARCH LETTERS 2 (1): - JAN-MAR 2007). I'm not sure that this link will work unless you have access to an academic database via a university etc., but here it is. Telleen-Lawton, the author of this opinion piece doesn't bother to cite a particular page for the article, but if you care to look you'll find it on page 4. How do Lobell and Field come to this conclusion? They assert that the crop yield would have been 2-3% higher if not for the influence of climate change.

For now, let's forgive Lobell and Field the absolutely staggering number of unsupported assumptions they make (read the article!), and let's instead read on. From 1982-1998, for example, the study concludes that climate trends let to an increase in the maize yield. The study doesn't consider any date from beyond 2002. In other words, the results of four years (1999-2002) are such an aberration from the general trend that they caused the results to be skewed negatively. The general trend was in fact positive over the majority of the period. Lobell and Field do assert that yields were likely to have been lower after 2002, but quite frankly admit that it's an untested conclusion. Part of the problem with this is of course that NASA has since had to revise its list of temperatures due to a a "mistake of calculation." It's no wonder few people know about it, considering the virtual news blackout. 1998 (which is included in the period with an overall climate related increase in yield) was in fact 1.24 degrees C above mean temperature, making it hotter than any year since. (1934 was hotter at 1.24 degrees above the mean.) Let's take a few more examples. 1987 was +0.81 degrees above the mean and 1990 was +0.88 degrees, but since 1998's high, only 1999 (+0.94) and 2006 (+1.08) have beaten these temperatures. While averages were certainly higher in the last decade, 2008 (+0.1) was colder than all years since 1982 except 1983, 1984, and 1997. Lobell and Field state that 2003-2005 were "three of the warmest five years in the past century." I did a quick count over NASA's figures for mean temperatures since 1903, and counted more than ten years which were hotter than the hottest of the three years (2005: +0.71). It should come as no surprise that the study Lobell and Field themselves cite for this bogus assertion was authored by the infamous global warming charlatan J Hansen.

Let's move on with Lobell and Field's study. In their conclusion they start strongly,

"recent climate trends, attributable to human activity, have had a discernible negative impact on global production of several major crops."
That sounds bad! They continue,
"The impact of warming was likely offset to some extent by fertilization effects of increased CO2 levels..."
Huh? So did crop yields decline or not? After some calculations, they offer the startling conclusion:
"the increase since 1981 corresponds to a roughly 3.5% yield increase, about the same as the 3% decrease in wheat yield due to climate trends over this period. Thus the effects of CO2 and climate trends have largely canceled each other over the past two decades, with a small net effect on yields."
Let me insert the word that Lobell and Field "accidentally" omitted: with a small net positive effect on yields. I could continue attacking this steaming pile of bovine faesces, but let's just cut to the chase. The study actually concludes that crop yields have increased by 0.5% over the period 1982-2002, but asserts that it should have increased by 3.5%, thus it claims that climate change has led to a 3% loss of the crop. *COUGH* This is the kind of "proof" that Telleen-Lawton relies upon for his own study.

Who is behind this study? The organization is called Environment America. It has roughly 120 employees and is described as an "environmental advocacy group." This Youtube clip probably tells you all you need to know about their political leanings. The Republicans are the "enemy". Another clip shows just how terribly young and earnest are most of the group's employees. It's also interesting (starting at 7:36 onwards) to note members of the group enthusiastically shaking the hand of disgraced ex-gov Blagojevich of Illinois.

The author of the report is Tim Telleen-Lawton. So far I've managed to discover that he was a junior at Stanford in 2004 working for Campus Greens. In fact he was actually the president of the organization at some point. He was still active in organizing protests and still a student at Stanford in 2006. In 2006 he was a "coterminal" student. Basically Stanford allows students who haven't quite finished their undergraduate degree to start a masters degree at the same time and complete them at the same time. So, as of 2006 we can say that he probably didn't yet have any degrees. The earliest he could possibly have graduated is 2006 with a masters degree. Every mention I find of him after this point refers to him as a "global warming advocate." Essentially he is a careerist greenie, with no experience in the real world beyond political activism. He himself describes his recent activities:

"After two years at Frontier Group and an exciting stint campaigning for Obama, I decided to move to DC to focus on passing a global warming cap-and-trade bill."
It's probably just a coincidence, but since everyone loves a good conspiracy theory I'll mention it anyway: Jim Tankersley, the author of the LA Times piece, also went to Stanford (graduating in 2000).
For more information, and some photos, of this "expert", have a look here and here.
Here he is. You would think the LA Times might care to investigate whether the author of a study is credible before they publish it, but I guess not:
Timothy Telleen-Lawton
Interestingly, the organization's website isn't functioning as of today. [Update: it seems to be working again.]

A much better study can be found here.