UPDATE: April 19 2011: See also the post by Anthony Watts Another significant land use effect found – sugar cane where the news article referred to in the post reads
“So far most of the thinking about ecosystem effects on climate considers only impacts from greenhouse gas emissions. But according to coauthor Greg Asner, “It’s becoming increasingly clear that direct climate effects on local climate from land-use decisions constitute significant impacts that need to be considered core elements of human-caused climate change.”
The abstract reads [boldface added]
“Albedo is an important factor affecting global climate, but uncertainty in the sources and magnitudes of albedo change has led to simplistic treatments of albedo in climate models. Here, the authors examine nine years (2000–08) of historical 1-km Moderate Resolution Imaging Spectroradiometer (MODIS) albedo estimates across South America to advance understanding of the magnitude and sources of large-scale albedo changes. The authors use the magnitude of albedo change from the arc of deforestation along the southeastern edge of the Brazilian Amazon (+2.8%) as a benchmark for comparison. Large albedo increases (>+2.8%) were 2.2 times more prevalent than similar decreases throughout South America. Changes in surface water drove most large albedo changes that were not caused by vegetative cover change. Decreased surface water in the Santa Fe and Buenos Aires regions of Argentina was responsible for albedo increases exceeding that of the arc of deforestation in magnitude and extent. Although variations in the natural flooding regimes were likely the dominant mechanism driving changes in surface water, it is possible that human manipulations through dams and other agriculture infrastructure contributed. This study demonstrates the substantial role that land-cover and surface water change can play in continental-scale albedo trends and suggests ways to better incorporate these processes into global climate models.”
This study supports our findings of a significant human effect on weather and climate through land use change in South America in our paper
Beltran-Przekurat, A., R.A. Pielke Sr., J.L. Eastman, and M.B. Coughenour, 2011: Modeling the effects of land-use/land-cover changes on the near-surface atmosphere in southern South America. Int. J. Climatol., accepted.
The abstract reads
GEMRAMS, a coupled atmospheric-biospheric model comprised of the Regional Atmospheric Modeling System and the General Energy and Mass Transport Model, was used to evaluate potential effects of land-use/land-cover changes (LULCC) on near-surface atmosphere over a southern South American domain. Several spring-early summer simulations were conducted using different land-cover scenarios representing current, natural, and afforestation conditions for this region for three periods, associated with El Niño- Southern Oscillation (ENSO) conditions. Changes in surface fluxes and the associated effects on near-surface temperature were spatially heterogeneous: different vegetation changes led to different effects. These changes were also associated with the seasonality of the vegetation. Conversion from grass to agriculture led to cooler, wetter near-surface atmospheric conditions. Warmer temperatures resulted from the conversion ofwooded grasslands or forest to agriculture. Afforestation resulted overall in cooler temperatures. For both LULCC scenarios the direction of the energy fluxes and temperature changes remained in general the same in two extreme ENSO years, although for some vegetation conversions the signal reversed direction. Overall, the impacts were enhanced during a dry year, i.e., 1999-2000, but the response also depended on the vegetation types involved in the conversion. The effects on precipitation were insignificant in the agriculture-conversion scenario. In simulated austral summer precipitation, the afforested scenario generated average increases of 1 mm day−1. The impacts were relatively higher for a “dry year”.
The Loarie et al 2011 study also provides support for the importance of dams and their effect on evaporation and transpiration from adjacent landscapes on local and regional climate that we reported on in
Hossain, F., I. Jeyachandran, and R.A. Pielke Sr., 2010: Dam safety effects due to human alteration of extreme precipitation. Water Resources Research, 46, W03301, doi:10.1029/2009WR007704.
Degu, A. M., F. Hossain, D. Niyogi, R. Pielke Sr., J. M. Shepherd, N. Voisin, and T. Chronis, 2011: The influence of large dams on surrounding climate and precipitation patterns. Geophys. Res. Lett., 38, L04405, doi:10.1029/2010GL046482.
The Loarie et al paper is also interesting as one of the authors, Chris Field, is a Co-Chair of Working Group II of the current IPCC assessment. In this position, he should be introducing the need for a broader perspective on the role of humans within the climate system. Unfortunately, however, this perspective needs to be also in Working Group I’s report since that is the foundation for the other IPCC reports.