Remember when solar alarmists said our sun would grow into a red giant? Never mind. It's corny!

He's done it again!

In the past, Anthony Watts from the denier blog WUWT has implied that because something hasn't happened yet it never will (to a ludicrous extent). He wants his readers to think that climate science is a hoax, or global warming won't be that bad and might even be good on balance. He's used evidence such as predictions that something is likely to happen in 60, 80, 100 years or more hasn't happened by today. It makes you wonder if he thinks he's immortal.

Today he's done it again, with one of his "Never Mind" headlines. This is one of his formulaic headlines, (another is "Claim:") which he uses to signal that he doesn't believe science. Note that in the USA, maize is called corn.

Headline: Remember when climate alarmists told us global warming was going to kill the U.S. corn crop? Never mind.

Well, when the "climate alarmists" (that's denier-speak for career scientists aka experts on their topic) they were talking about the future. Hence my headline. Just because the sun isn't a red giant yet, it doesn't mean it won't happen around the time predicted.

Anthony's opening lines referred to two recent papers at which one of his more prolific denier writers (Eric Worrall) scoffed in the past. Anthony wrote:

You may remember seeing scare stories like these in the media.

• Claim: Climate Change will Cause a Global Corn Crop Failure [Tigchelaar18]
• Global Warming Will Cut Crop Yields – Assuming No Adaption [Zhao17]

Reality bites in two ways; 1. Actual data shows yield increases, and 2. New study says warming has actually helped corn yields.

In the above quote, I've added a reference and link to the papers Eric Worrall was supposedly writing about. As you've come to expect, denier blogs are aimed to mislead not inform, so there are a few points to note:

About his scare stories:

• The first paper, Tigchelaar18, was referring to the future, when the world reaches 2°C and  4°C warming. In fact, about the present, the authors said the chance of there being a global drop in production of more than 10% is about nil.
• The second paper, Zhao17, was also reporting production estimates of the future, the second half of the century and beyond. It found the loss in maize yield for each degree Celsius increase in global mean temperature in the future is around 7.4 +/- 4.5%. They found some variation between countries with the loss in the USA being greater (a loss of 10.3 +/- 5.4% for each degree Celsius increase). The losses quoted only relate to the impact of temperature increase and do not allow for changes in other factors such as genetic improvements, elevated atmospheric CO2 concentration or changes in rainfall.

Reality bites, for sure:

• There was probably only one thing in the above quote that Anthony got right, actual data shows yield increases over the past few decades in the USA.
• His second reality bites point is misleading. It's not so much that warming has helped corn yields, it's that corn farmers have adapted to global warming.

Peculiarly pleasant weather for US maize

The new paper, is by Ethan E Butler, Nathaniel D. Mueller, and Peter Huybers and has the title: Peculiarly pleasant weather for US maize. The authors say that recent work indicates the increasing yield trends in maize are linked to earlier planting and choosing longer maturing varieties. What they say they found was that although studies haven't found any evidence of adaptation to historical changes in climate in the USA, this may not be so. At the regional level, there is evidence that farmers are adapting to to the changing climate. They add that farmers are careful in apportioning weather-related risks as shown by the pattern of insurance coverage.

They point out that although earlier planting means the crop is exposed to lower temperatures early in the growing season, this is counterbalanced by warmer weather in later growth, when the grain is being filled. All of that is beneficial on the whole, because as the authors say "yield is more than 10 times more sensitive to growing degree days (GDDs) during grain filling".

The researchers looked at whether farmers were actually making adjustments to changes in climate. If adaptation is occurring, then there should be higher yields under current climate conditions than there were under earlier climate conditions. They referred to the use of longer maturing cultivars and the timing of planting and said:

The only year in the last decade with notable yield loss from the recent development schedule is 2012, when extreme heat occurred during early grain filling, the most sensitive period of development....

...The combined effects of changes in climate and crop timing lead to further yield increases that constitute a modest but statistically significant adaptation to climate change. Together, these improvements represent more than a quarter of Midwestern trends in maize yield since 1981.

The authors warn that this might not last. They said that historical improvements in yield have had more to do with improvements in climate than was previously thought and that purely technological improvements are smaller than previously thought. Thing is, this might not last. As the temperature continues to increase and CO2 levels also increase, things could change. In the future, farmers might need to grow faster maturing varieties, albeit still planting them earlier. That would be to avoid excessive heat later in the season. Just the same, in the shorter term, farmer adaptations along with the longer growing season might help to keep the yield improving.

Sudden bursts of heat will kill the crop

I found an older paper (from 2002) that talked about the problems higher temperatures posed to maize production. One thing they found was that photosynthesis was inhibited when leaf temperatures were above 38°C, and that sudden bursts of higher temperatures was much worse than when temperatures increased gradually.

CO2 enhancement may not last with C3 and C4 crops

I'm sure there is a lot more research that could be discussed; however I'll just mention another paper published recently in the journal Science. In that work, the authors point out that theory and observation indicates that C4 plant species (such as maize) benefit less from rising carbon dioxide concentrations than C3 species. A long-term CO2 enrichment study over 20 years found this may not hold true forever. From the article:

Over the first 12 years, biomass increased with elevated CO2 in C3 plots but not C4 plots, as expected. But over the next 8 years, the pattern reversed: Biomass increased in C4 plots but not C3 plots. Thus, even the best-supported short-term drivers of plant response to global change might not predict long-term results.

Anthony Watts got ahead of himself

To recapitulate, Anthony Watts has jumped the gun and thinks that because yield has not yet reduced, it won't reduce in the future and there's no need to worry about food or feed shortages. (He doesn't say how he thinks the problem of feeding the world in the future will be resolved, when the population hits 9 billion or more. The best minds, of which Anthony's is not one, have been working on that problem for some time.)

From the WUWT comments

There were quite a few thoughts voicing complaints about things like an assumption that CO2 is a greenhouse gas, or that the press release didn't focus on "CO2 is planned food".

Paul Penrose complained about "the whole CAGW movement":

November 5, 2018 at 3:30 pm
They say that the changing climate as helped increase yields, but then they add the obligatory disclaimer that the benefit may not last. So it’s OK to show some doubt in this case, but we can’t doubt the climate forecasts (models)? You have to wonder if they would have made that kind of disclaimer before the whole CAGW movement took over this area of science.

Michael might not know the difference between the photosynthetic pathways of C3 and C4 plants.

November 5, 2018 at 3:31 pm
Why no mention of the “Greening””effect of more CO2 ?
MJE

Charles Higley is similarly confused about a number of things biological and atmospheric.

November 5, 2018 at 4:02 pm
Exactly. They purposely ignore the elephant in the room and the fact that higher CO2 probably makes corn able to germinate and grow at lower temperatures, meaning that the farmers can plant earlier, even without any detectable warming.

Curious George felt sorry for Michael and Charles, and tried to set them straight.

November 5, 2018 at 5:47 pm
Corn is a C4 plant – it spends some energy in concentrating CO2, giving it a considerable advantage over C3 plants when CO2 is scarce. The “greening” effect of an increased concentration of CO2 benefits primarily C3 plants.

Mark Lee hasn't looked at a global surface temperature chart, probably since 1970, going by this comment:

November 5, 2018 at 3:37 pm
I think the article is in error as to the cause of the growth, at least in this century. Since temperatures haven’t gone up to any appreciable degree for the last 20 years, shouldn’t the continuing, if not the prior decades of increased yield be attributed to rising CO2 and not temperature?

Jeff is what you might call a classic or pure denier:

November 5, 2018 at 6:01 pm
Life’s majesty grows grander and grander the closer you are to the equator.
More species, higher net primary productivity.
And these are the warmest areas on earth.
We have nothing to fear from warming, in fact it will be a net benefit.

References and further reading

Ethan E. Butler, Nathaniel D. Mueller, Peter Huybers. "Peculiarly pleasant weather for US maize." Proceedings of the National Academy of Sciences Nov 2018, 201808035; DOI: 10.1073/pnas.1808035115 (early release here)

Tigchelaar, Michelle, David S. Battisti, Rosamond L. Naylor, and Deepak K. Ray. "Future warming increases probability of globally synchronized maize production shocks." Proceedings of the National Academy of Sciences Jun 2018, 115 (26) 6644-6649; DOI: 10.1073/pnas.1718031115. (pdf here)

Zhao, Chuang, Bing Liu, Shilong Piao, Xuhui Wang, David B. Lobell, Yao Huang, Mengtian Huang et al. "Temperature increase reduces global yields of major crops in four independent estimates." Proceedings of the National Academy of Sciences 114, no. 35 (2017): 9326-9331. (pdf here)

Crafts-Brandner, Steven J., and Michael E. Salvucci. "Sensitivity of photosynthesis in a C4 plant, maize, to heat stress." Plant physiology 129, no. 4 (2002): 1773-1780. doi: [10.1104/pp.002170]

Reich, Peter B., Sarah E. Hobbie, Tali D. Lee, and Melissa A. Pastore. "Unexpected reversal of C3 versus C4 grass response to elevated CO2 during a 20-year field experiment." Science 360, no. 6386 (2018): 317-320. DOI: 10.1126/science.aas9313

Anthony Watts, the seer, goes time traveling to 2041 and beyond, HotWhopper, May 2015.