Abstract
Abstract. Identifying and quantifying the sources of climate impacts from land use and land cover change (LULCC) is necessary to optimize policies regarding LULCC for climate change mitigation. These climate impacts are typically defined relative to emissions of CO2, or sometimes emissions of other long-lived greenhouse gases. Here we use previously published estimates of the radiative forcing (RF) of LULCC that include the short-lived forcing agents O3 and aerosols, in addition to long-lived greenhouse gases and land albedo change, for six projections of LULCC as a metric for quantifying climate impacts. The LULCC RF is attributed to three categories of LULCC activities: direct modifications to land cover, agriculture, and wildfire response, and sources of the forcing are ascribed to individual grid points for each sector. Results for the year 2010 show substantial positive forcings from the direct modifications and agriculture sectors, particularly from south and southeast Asia, and a smaller magnitude negative forcing response from wildfires. The spatial distribution of future sources of LULCC RF is highly scenario-dependent, but we show that future forest area change can be used as a predictor of the future RF from direct modification activities, especially in the tropics, suggesting that deforestation-prevention policies that value land based on its C-content may be particularly effective at mitigating climate forcing originating in the tropics from this sector. However, the response of wildfire RF to tropical land cover changes is not as easily scalable and yet imposes a non-trivial feedback onto the total LULCC RF.
Highlights
Global land use and land cover change (LULCC) is recognized as an important element of past and future anthropogenic climate changes (Feddema et al, 2005; van der Werf and Peterson, 2009; Foley et al, 2011)
The major source of positive forcing from direct modifications to the land cover is from CO2 emissions, with a minor negative forcing from albedo change and small contributions from aerosols and non-CO2 greenhouse gases
Fertilizer application drives both a positive forcing, as N2O emissions, and a negative forcing, through fertilizing natural vegetation after transport and deposition of N and drawing down CO2 from the atmosphere. We find that these forcings partially cancel each other out and the differences in the agricultural radiative forcing (RF) between future scenarios are mainly driven by emissions of CH4 from livestock and rice cultivation
Summary
Global land use and land cover change (LULCC) is recognized as an important element of past and future anthropogenic climate changes (Feddema et al, 2005; van der Werf and Peterson, 2009; Foley et al, 2011). The Reducing Emissions from Deforestation and Forest Degradation (REDD) program is a one such effort that seeks to lower anthropogenic greenhouse gas emissions from deforestation using financial incentives to maintain or increase forest area (Lubowski and Rose, 2013). Changes in forest area modify the land surface biophysics (such as albedo) and emissions of short-lived species: aerosols and precursors to ozone formation. Clear-cutting of extra-tropical forest emits CO2 and reveals the land surface underlying the forest canopy that, when snow-covered, is highly reflective.
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