Comparison of agricultural impacts of climate change calculated from high and low resolution climate change scenarios: Part II. Accounting for adaptation and CO2 direct effects

We assert that the simulation of fine-scale crop growth processes and agron omic adaptive management using coarse-scale climate change scenarios lower confidence in regional estimates of agronomic adaptive potential. Specifica lly, we ask: 1) are simulated yield responses to low-resolution climate cha nge, after adaptation (without and with increased atmospheric CO2), signifi cantly different from simulated yield responses to high-resolution climate change, after adaptation (without and with increased atmospheric CO2)? and 2) does the scale of the soils information, in addition to the scale of the climate change information, affect yields after adaptation? Equilibrium (1 x CO2 versus 2 x CO2) climate changes are simulated at two different spati al resolutions in the Great Plains using the CSIRO general circulation mode l (low resolution) and the National Center for Atmospheric Research (NCAR) RegCM2 regional climate model (high resolution). The EPIC crop model is use d to simulate the effects of these climate changes; adaptations in EPIC inc lude earlier planting and switch to longer-season cultivars. Adapted yields (without and with additional carbon dioxide) are compared at the different spatial resolutions. Our findings with respect to question 1 suggest adapt ation is more effective in most cases when simulated with a higher resoluti on climate change than its more generalized low resolution equivalent. We a re not persuaded that the use of high resolution climate change information provides insights into the direct effects of higher atmospheric CO2 levels on crops beyond what can be obtained with low resolution information. Howe ver, this last finding may be partly an artifact of the agriculturally beni gn CSIRO and RegCM2 climate changes. With respect to question 2, we found t hat high resolution details of soil characteristics are particularly import ant to include in adaptation simulations in regions typified by soils with poor water holding capacity.