A Free-Market Energy Blog

‘Climate and Agriculture: We’re Not Dumb’ Follow-Up

By Chip Knappenberger -- April 11, 2009

In one of my first posts for MasterResource, I discussed a (then) just-published paper in Science magazine by David Battisti and Rosamond Naylor that argued that global warming was fast leading us into agricultural failure and a global food crisis.

I pointed out that this was a naïve analysis that gave short-shrift to our ability to adapt to changing climate conditions. Through technological improvement of farming practices and the development of new crop varieties, farmers have not only been able to keep up with a changing climate, but have also managed to produce ever-greater crop yields.

Far from being “dumb farmers” who stand idly by and watch their crops fail, farmers and crop scientists continually work to bring more and better crops to market. This is how it has been in the past, is currently, and undoubtedly will be in the future. After all, it is in all of our best interests—we have to eat.

It seems I wasn’t the only one who had such problems with the Battisti and Naylor article. In this week’s Science magazine is a letter to the editor that makes these very same points.

A group of scientists from the School of the Environment and Natural Resources at the U.K.’s Bangor University, led by Neal Hockley, wrote in to point out the weakness of Battisti and Naylor’s conclusions concerning the threat of climate change to global food security:

If the currently extreme temperatures become the norm, then we would expect farmers to adapt, maintaining yields by selecting alternative crop varieties, species, and cultivation techniques. Examining the performance of agriculture under unprecedented conditions [as Battisti and Naylor did] tells us little about how it will adapt to future climates.

Hockley and colleagues go on to explain that their concern lies more with potential changes in climate variability than with changes in the mean climate, because high year-to-year variability makes it challenging to select the proper crop varieties and/or species most appropriate for the weather in a particular year. However, they think that even changes in variability can be overcome with improved long-range forecasts. Ultimately they conclude:

The future productivity of world agriculture will therefore depend on whether the development and adoption of new varieties and techniques can keep pace with the changing climate and whether improvements in long-range forecasting can keep pace with increases in interseasonal variation. Commercial interests will probably ensure this happens for major crops and richer countries, but substantial public service breeding will be needed for minor crops that are currently prevalent in many tropical areas.

Just as I thought. We’ll find a way to keep our major food crops flourishing, and with a little extra effort, so too will it be for our minor crops.


Battisti, D.S., and R.L. Naylor, 2009. Historical warnings of future food insecurity with unprecedented seasonal heat. Science, 323, 240-244.

Hockley, N., Gibbons, J.M., and G. Edwards-Jones, 2009. Risks of Extreme Heat and Unpredictability. Science, 324, 177.


  1. Ed Reid  

    The Battisti and Naylor paper appears to presume the existence of a climatological hockey stick. The Hockley, Gibbons and Edwards-Jones paper then appears to presume that the blade of the hockey stick is shaped like a sine wave, with fluctuations about a rapidly increasing underlying temperature trend. Both presumptions are questionable at best.

    At its peak, the surface temperature anomaly was ~+0.7 C. The current anomaly is less than half that level. The surveys of US temperature measuring stations reported at http://www.surfacestations.org demonstrate that more than half of the stations are subject to measurement errors in excess of 2 C, based on the NCDC Climate Reference Network Rating Guide. Only 11% of the stations surveyed appear to be subject to errors of less than 1 C on the same basis.

    Based on the measurements reported from these stations, we are presented with temperature series reported to two decimal place “accuracy”, after the actual measured data has been massaged through multiple “black box” computer programs.

    Combining these pieces of information, we realize that what is being reported is a global average surface temperature of ~14.21 +/- 2+ C. (Actually, it might well be 14.21 – 2+ C, since most of the error would be anticipated to be positive, based on the site surveys.) This realization is hardly the basis for great confidence in the reported temperatures or temperature trends. It is certainly not an adequate basis for the investment of ~$30 trillion over the next 40 years in the US to reduce US carbon emissions by 80%; or, for the investment of ~$100 trillion to achieve that carbon emissions reduction globally.

    Temperature is certainly not the easiest thing to measure accurately. However, my experience tells me that one of the premier scientific organizations in the US government ought to be capable of measuring temperatures with the accuracy with which they later report them. Either that, or they should immediately stop reporting temperatures including insignificant digits. Based on the survey results regarding the surface temperature measuring stations, I am not convinced that the digit to the left of the decimal place is significant, no less the two digits to the right of the decimal place.


  2. Andrew  

    It seems intuitively obvious to me that we can pretty easily figure out how to cope with climate change’s effect on crops-we have strategies in place already to deal with weather extremes, and we understand exactly when and where certain crops grow because of the climatic conditions at those times and in those places. What’s more, technology has always advanced our ability to raise yields. Better harvesting techniques/machinery, better pesticides, and now even genetically modified crops. What is probably much more interesting-and worth studying-is the effect of agriculture on climate.


  3. E.M.Smith  

    The major limit to crop growth is frost, not heat. An existence proof of sorts is Phoenix, Arizona. My Sunset Garden Book shows that only during the peak heat of the 2 to 3 mid summer months is there a significant limit on what can be grown (it recommends heat tolerant varieties for those months).

    What this means is rather simple: Assuming warming is happening and continues, places with short growing seasons will get longer growing seasons right up until they match Southern California (which has year round growth). Then as they rise in temperatures to match the center of one of the hottest deserts in north America, and only then, will their summer months heat start to depress the growth of selected plants such that they drop to “only” a 9 month growing season for cool season plants. (They will still be able to grow hot tolerant plants like tomato, peppers, nopales (cactus), tepary beans, citrus, millet, etc. during those months).

    The conclusion from this is simple: Since most of the growing regions of the planet are frost limited to far less than 9 month growing seasons, the world food supply will increase with increasing warmth as the growing season expands until such time as they reach temperatures of about 120 F + (which is not exactly on the cards per the IPCC projections…).

    It is also the case that increased CO2 promotes more yield even with no increase in water (it defends against water stress). To the extent CO2 increase, we get more food.

    The notion that global warming means less food is simply broken.

    Also, per the question of precision in the temperature series: I’ve looked at the GIStemp computer code. It gets temperatures in degrees F with 2 digits to the right of the decimal from NOAA. It is NOAA who introduces the false precision. The NOAA data are measured in F.x then recorded as whole degrees F (the tenths are discarded on the forms sent in to NOAA). Thus no precision greater than whole degrees F is possible. Averaging a set of different temperatures together is NOT oversampling of a single thing, so you can not claim that oversampling is letting you recover more precision (each day is a discreet event, sampled once). While GISS ought to take the NOAA data and discard everything to the right of the decimal, they do not. They convert it to C.x degrees Centigrade in tenths. This preserves the original false precision to some extent. They then do a great deal of math on the data that will NOT preserve precision well. IMHO, at the end of their process there is nothing to the right of the decimal that is of merit and the first digit to the left of the decimal is certainly suspect.

    Also, FWIW, I’ve put together a posting that shows we have no need to deny ourselves the benefit of using oil or coal now. We will never run out of energy and never run out of ‘petro’chemicals:


    Finally, loved the guest article at WUWT! Like what I see here too.


  4. techreseller  

    I do believe that the issue of climate change is undecided. However, I also believe that a number of the comments above are missing some crucial aspects if the climate is indeed warming up on general basis. Farmers tend to own their land and thus have fixed costs and places where they can farm. In the short run (which can be from 2-10 years), an increase in temperature may negatively affect their ability to grow the crops that their land and equipment is configured for. As the growing bands moves north (assuming Northern Hemisphere and warming) then the crops that grow well in various places change. The modification of crops will take time and will lag the “growing bands” change. The other issue surrounds coastal growing areas. If seas do indeed rise then salt infiltration into the fields is a large problem in the soils fertility. An example is the Eastern Shore of MD and VA. Tomatoes are a huge crop there. If the seas rise, salt will infiltrate those fields making them unsuitable for tomato crops.


Leave a Reply