Effects of land cover change on temperature and rainfall extremes in multi-model ensemble simulations

A J Pitman,M G Donat,V Brovkin,L V Alexander,N De Noblet-Ducoudré,J.-P Boisier,C Delire,F B Avila,V Gayler,B Van Den Hurk,F Cruz,A Voldoire,C Reick

doi:10.5194/esd-3-213-2012

Abstract

Abstract. The impact of historical land use induced land cover change (LULCC) on regional-scale climate extremes is examined using four climate models within the Land Use and Climate, IDentification of robust impacts project. To assess those impacts, multiple indices based on daily maximum and minimum temperatures and daily precipitation were used. We contrast the impact of LULCC on extremes with the impact of an increase in atmospheric CO2 from 280 ppmv to 375 ppmv. In general, consistent changes in both high and low temperature extremes are similar to the simulated change in mean temperature caused by LULCC and are restricted to regions of intense modification. The impact of LULCC on both means and on most temperature extremes is statistically significant. While the magnitude of the LULCC-induced change in the extremes can be of similar magnitude to the response to the change in CO2, the impacts of LULCC are much more geographically isolated. For most models, the impacts of LULCC oppose the impact of the increase in CO2 except for one model where the CO2-caused changes in the extremes are amplified. While we find some evidence that individual models respond consistently to LULCC in the simulation of changes in rainfall and rainfall extremes, LULCC's role in affecting rainfall is much less clear and less commonly statistically significant, with the exception of a consistent impact over South East Asia. Since the simulated response of mean and extreme temperatures to LULCC is relatively large, we conclude that unless this forcing is included, we risk erroneous conclusions regarding the drivers of temperature changes over regions of intense LULCC.

Highlights

The Land Use and Climate, IDentification of robust impacts (LUCID) project is a major international effort to understand the biophysical impacts of land use induced land cover change (LULCC)
CSDI in ECHAM5 is consistently insensitive to LULCC, which may in part be due to the lower intensity of the LULCC (Fig. 1) the relationship between the scale of LULCC and its impact on indices such as CSDI are Figure 6 unknown
The impact of LULCC on regional-scale climate averages has been thoroughly studied and a significant impact on the mean temperature should be anticipated over regions of intense LULCC (Pielke et al, 2011)

Summary

Introduction

The Land Use and Climate, IDentification of robust impacts (LUCID) project (de Noblet-Ducoudreet al., 2012) is a major international effort to understand the biophysical impacts of land use induced land cover change (LULCC). LUCID focussed on one major type of LULCC: conversion of land between forests, pasture and crops. How LULCC affects land–atmosphere interactions is complex because a major change to land cover has competing impacts. LULCC, in the form of clearance for crops and pasture, affects net radiation and the partitioning of available energy at the surface. Since conversion of native vegetation to crops and pasture typically increases albedo, it reduces net radiation (Forster et al, 2007) which tends to cool the surface. Changes in leaf area index, aerodynamic roughness length, stomatal conductance and the seasonality of vegetation cover tend to decrease evapotranspiration and increase sensible heat fluxes

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