Our workshop report on the role of humans in the climate system appeared in late 2007;
Mahmood, R., K. G. Hubbard, R. Pielke Sr. (2007), Effect of Human Activities on the Atmosphere,Eos Trans. AGU, 88(52), 580, 10.1029/2007EO520007
The abstract reads,
“Detecting the Atmospheric Response to the Changing Face of the Earth: A Focus on Human-Caused Regional Climate Forcings, Land-Cover/Land-Use Change, and Data Monitoring; Boulder, Colorado, 27–29 August 2007; Human activities continue to significantly modify the environment. The impacts of these changes are highlighted, for example, in local-, regional-, and global-scale trends in modern atmospheric temperature records and other relevant atmospheric indicators. Studies using both modeled and observed data have documented these impacts. Thus, it is essential that we detect these changes accurately to better understand the impacts on climate and provide improved assessment of the predictability of future climate.”
The full EOS workshop report is also available (see).
There is a new meeting scheduled in November 2008 which will further present assessments of the role of land surface processes within the climate system. It is
“LUCID – Land-Use and Climate, IDentifi cation of robust impacts” organized by Nathalie de Noblet-Ducoudré and Andy Pitman.
This meeting will be a major, much needed further reporting on this issue, but only if they assess climate metrics more completely than was done in the 2007 IPCC report.
In assessing the role of land use change, I have urged them to consider the three climate metrics that we have proposed:
1. The magnitude of the spatial redistribution of latent and sensible heating as we presented in
Chase, T.N., R.A. Pielke, T.G.F. Kittel, R.R. Nemani, and S.W. Running, 2000: Simulated impacts of historical land cover changes on global climate in northern winter. Climate Dynamics, 16, 93-105.
2. The magnitude of the spatial distribution of precipitation and moisture convergence as we reported in
Pielke, R.A. Sr., and T.N. Chase, 2003: A Proposed New Metric for Quantifying the Climatic Effects of Human-Caused Alterations to the Global Water Cycle. Presented at the Symposium on Observing and Understanding the Variability of Water in Weather and
and
3. The normalized gradient of regional radiative heating changes (which we did for aerosols in
Matsui, T., and R.A. Pielke Sr., 2006: Measurement-based estimation of the spatial gradient of aerosol radiative forcing. Geophys. Res. Letts., 33, L11813, doi:10.1029/2006GL025974).
In the aerosol evaluation, we found that in terms of the gradient of atmospheric radiative heating, the role of human inputs was 60X greater than the role of the human increase in the well-mixed greenhouse gases. This means, that with respect to the effect on atmospheric circulations, the aerosol effect (and I anticipate land use change also) has a much more significant role on the climate than is inferred when using global average metrics.
Also, the pre-industrial crop areas that are being used (see their figure of crop area) relative to current crops, is going to mute the signal in all areas but most significantly in Asia, Africa and Europe. I have suggested that they complete a natural landscape set of runs. After all, the CO2 runs are made from “natural” to “current” so that the landscape change runs should made consistent with that difference, even if not over the same time period. Both sets of experiments will be insightful but the the assessment is significantly incomplete if the natural landscape simulations are not also completed.
Their LUCID meeting should be a very important assessment. However, it is essential that they move beyond the standard global average procedure (as emphasized in the IPCC report) to evaluate the human role on the climate system, as well as to complete natural landscape simulations. Their assessment must also focus on how the heterogeneous effects of landscape change alter atmospheric and ocean circulation patterns (as suggested by items #1, #2 and #3). It is these regional responses, not a global average, that produces drought, floods and other societally important climate impacts.