title: Observed increase in local cooling effect of deforestation at higher latitudes.
abstract: Deforestation in mid- to high latitudes is hypothesized to have the potential to cool the Earth's surface by altering biophysical processes. In climate models of continental-scale land clearing, the cooling is triggered by increases in surface albedo and is reinforced by a land albedo-sea ice feedback. This feedback is crucial in the model predictions; without it other biophysical processes may overwhelm the albedo effect to generate warming instead. Ongoing land-use activities, such as land management for climate mitigation, are occurring at local scales (hectares) presumably too small to generate the feedback, and it is not known whether the intrinsic biophysical mechanism on its own can change the surface temperature in a consistent manner. Nor has the effect of deforestation on climate been demonstrated over large areas from direct observations. Here we show that surface air temperature is lower in open land than in nearby forested land. The effect is 0.85 ± 0.44 K (mean ± one standard deviation) northwards of 45° N and 0.21 ± 0.53 K southwards. Below 35° N there is weak evidence that deforestation leads to warming. Results are based on comparisons of temperature at forested eddy covariance towers in the USA and Canada and, as a proxy for small areas of cleared land, nearby surface weather stations. Night-time temperature changes unrelated to changes in surface albedo are an important contributor to the overall cooling effect. The observed latitudinal dependence is consistent with theoretical expectation of changes in energy loss from convection and radiation across latitudes in both the daytime and night-time phase of the diurnal cycle, the latter of which remains uncertain in climate models.
authors.affiliation: School of Forestry and Environmental Studies, Yale University, New Haven, Connecticut 06511, USA. xuhui.lee@yale.edu
authors.forename: Xuhui
authors.initials: X
authors.lastname: Lee
authors.forename: Michael L
authors.initials: ML
authors.lastname: Goulden
authors.forename: David Y
authors.initials: DY
authors.lastname: Hollinger
authors.forename: Alan
authors.initials: A
authors.lastname: Barr
authors.forename: T Andrew
authors.initials: TA
authors.lastname: Black
authors.forename: Gil
authors.initials: G
authors.lastname: Bohrer
authors.forename: Rosvel
authors.initials: R
authors.lastname: Bracho
authors.forename: Bert
authors.initials: B
authors.lastname: Drake
authors.forename: Allen
authors.initials: A
authors.lastname: Goldstein
authors.forename: Lianhong
authors.initials: L
authors.lastname: Gu
authors.forename: Gabriel
authors.initials: G
authors.lastname: Katul
authors.forename: Thomas
authors.initials: T
authors.lastname: Kolb
authors.forename: Beverly E
authors.initials: BE
authors.lastname: Law
authors.forename: Hank
authors.initials: H
authors.lastname: Margolis
authors.forename: Tilden
authors.initials: T
authors.lastname: Meyers
authors.forename: Russell
authors.initials: R
authors.lastname: Monson
authors.forename: William
authors.initials: W
authors.lastname: Munger
authors.forename: Ram
authors.initials: R
authors.lastname: Oren
authors.forename: Kyaw Tha
authors.initials: KT
authors.lastname: Paw U
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Richardson
authors.forename: Hans Peter
authors.initials: HP
authors.lastname: Schmid
authors.forename: Ralf
authors.initials: R
authors.lastname: Staebler
authors.forename: Steven
authors.initials: S
authors.lastname: Wofsy
authors.forename: Lei
authors.initials: L
authors.lastname: Zhao
mesh_terms: D000388:Air / Q000032:analysis; D000531:Altitude; D001272:Atmosphere / Q000032:analysis; D055592:Biophysical Phenomena; D002170:Canada; D002980:Climate; D003247:Conservation of Natural Resources; D016468:Forestry; D012621:Seasons; D013696:Temperature; D014197:Trees / Q000254:growth & development*; D014481:United States
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