date: Tue Nov 28 10:03:41 2000
from: Tim Osborn <t.osbornatXYZxyz.ac.uk>
subject: Re: MAFF presentation
At 09:26 28/11/00 -0000, you wrote:
>It would be helpful if you could let me know where you are with
>the analysis; I couldn't remember if you had completed analysing the
>exceedances for response thresholds and passed them on to David yet
>or were still working on the last of the daily/monthly ones.
>Can I have a quick update please and an ETA.
My e-mail to you and Martin on the 14th November explained that we had finished the response thresholds analysis, simply because the *none* of the thresholds were exceeded. The weather/climate "events" related to the response thresholds were expressed by the agricultural specialists in terms of mean temperature, precipitation and CO2 changes only - as was already known, I think, the mean climate changes for the UK are not expected to impact upon UK agriculture in a large enough manner to breach the economic response thresholds. The first half of my e-mail dealt with this issue and I've repeated it below. So that's the response thresholds dealt with.
What I'm doing now (today) is to finish generating scenarios of the 4 remaining force thresholds (the ones I never got done in time for the October meeting). On Thursday or Friday I will then identify the year in which each of the 20 or so force threshold events pass the 0.1 or 0.5 levels, under the HadCM2 scenario that I've used for all the analyses. Since I know the global climate change (temperature) for each year of this simulation, I will be able to plot the scenarios against global temperature rather than against time (year) and identify what global temperature change should be avoided if certain thresholds are to be avoided (lots of uncertainties have built up by this point of course!). David can then use MAGICC to come up with alternative (reduced) emissions scenarios that avoid global temperature changes reaching the critical levels thus identified - and then we know what steps the global community need to take to save the UK cauliflower industry! :-)
David and I have finished reading the 60 pages of the response threshold reports. We have attempted to extract the climate changes that cause the economic response thresholds to be exceeded, for the five crop types used by Rounsevell and Jones.
(1) Winter wheat. Harrison and Butterfield show responses to a range of variables (temperature, precipitation, solar radiation, vapour pressure, wind), but few of them change sufficiently in the climate change scenarios to even approach the threshold values. The exception is temperature, where winter warming on its own would be enough to lower yields and breach thresholds. *But*, winter precipitation and enhanced CO2 (Wheeler) offset the lower yields and prevent any thresholds from being reached.
(2) Winter/spring barley. Harrison and Butterfield show that warming will enhance yields, but not enough to breach upper thresholds. Precipitation is unimportant. No lower thresholds will be breached either.
(3) Grass ley. Warming will increase yield, so no lower thresholds are breached and Rounsevell and Jones do not define any upper thresholds.
(4) Sugar beet. For reasonable levels of climate change, no cases reach even a 10% decrease in yield, so no thresholds are breached.
(5) Lettuce. Wheeler's table 5 indicates yield reduction thresholds can be exceeded by temperature changes that are realisable. But when CO2 changes are also included (tables 6 & 7), yields are kept well above the thresholds. None will be breached.
Do you have any comments on the above? Feel free to distribute this summary amongst the group.