IGSM-TEM Land use in CAM3.1-CLM3.0: Impacts of Land use and biofuels policy on climate

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Hallgren, Willow
Schlosser, Adam
Monier, Erwan
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Chan, F.

Marinova, D.

Anderssen, R.S

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2011
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Perth, Australia

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Abstract

The impact on climate of future land use and energy policy scenarios is explored using two economicallymodelled land-use frameworks: (i) Pure Cost Conversion Response (PCCR), or 'deforestation', where the price of land constrains agricultural conversion, including growing biofuels, and; (ii) Observed Land Supply Response (OLSR), or 'intensification', where legal, environmental and other constraints encourage more intense use of existing agricultural land (i.e. less forest clearing). These two land-use frameworks were used to explore how the large scale plantation of cellulosic biofuels to meet global energy demand impacts the future climate. The land cover of the Community Atmospheric Model Version 3.0 (CAM3.0) was manipulated to reflect these four different land use and energy scenarios (i.e. PCCR and OLSR with and without biofuels). CAM3.0 was run to equilibrium, under 1990 and 2050 climate conditions, in order to assess the impact these land cover changes have on the atmospheric state. For the 2050 climate conditions, CAM was prescribed with concentrations of radiatively active trace gases (a.k.a. greenhouse gases) that result from a moderate stabilization target by the end of the 21st century. Overall in the extratropics, the intensification and deforestation scenarios increase the land-surface reflectivity over many areas of the globe, indicating that biofuel cropland is replacing darker land-vegetation types, decreasing absorption of solar radiation, which leads to a cooling effect. These patterns are strongest in the northern hemisphere, and occur to a greater extent in the PCCR scenarios. Moreover, the cooling is strongest when a biofuel policy is implemented. These temperature changes are for the most part overwhelmed by the trace-gas forcing (i.e. anthropogenic warming). However, in some regions, land surface changes in the PCCR case can counteract or notably lessen the warming. In much of the Amazonian and African tropics, however, the PCCR deforestation leads to a decrease in evaporative fraction, and an increase in sensible heat flux, leading to a warming effects over regions where biofuels have replaced tropical forests. These local, land-use induced changes in surface heat fluxes have non-local impacts on cloudiness and precipitation, the majority of which occur over oceans. The majority of the precipitation results show patterns which counteract those due to trace-gas forcing. We conclude that the implementation of a future energy policy where biofuels play a significant part, as well as the way we price land and the constraints placed on deforestation, both have a statistically significant impact on climate in 2050, and the land use change which led to the largest replacement of forested lands with biofuel cropland had the largest latitudinally-dependent impact on temperatures around the world.

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MODSIM 2011, 19th International Congress on Modelling and Simulation

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© 2011 Modellling & Simulation Society of Australia & New Zealand. The attached file is reproduced here in accordance with the copyright policy of the publisher. For information about this conference please refer to the conference’s website or contact the author(s).

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Environmental Impact Assessment

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