Impact of vegetation feedback on the temperature and its diurnal range over the Northern Hemisphere during summer in a 2 × CO2 climate

Abstract

This study examines the potential impact of vegetation feedback on the changes in the diurnal temperature range (DTR) due to the doubling of atmospheric CO 2 concentrations during summer over the Northern Hemisphere using a global climate model equipped with a dynamic vegetation model. Results show that CO 2 doubling induces significant increases in the daily mean temperature and decreases in DTR regardless of the presence of the vegetation feedback effect. In the presence of vegetation feedback, increase in vegetation productivity related to warm and humid climate lead to (1) an increase in vegetation greenness in the mid-latitude and (2) a greening and the expansion of grasslands and boreal forests into the tundra region in the high latitudes. The greening via vegetation feedback induces contrasting effects on the temperature fields between the mid-and high-latitude regions. In the mid-latitudes, the greening further limits the increase in T max more than T min , resulting in further decreases in DTR because the greening amplifies evapotranspiration and thus cools daytime temperature. The greening in high-latitudes, however, it reinforces the warming by increasing T max more than T min to result in a further increase in DTR from the values obtained without vegetation feedback. This effect on T max and DTR in the high latitude is mainly attributed to the reduction in surface albedo and the subsequent increase in the absorbed insolation. Present study indicates that vegetation feedback can alter the response of the temperature field to increases in CO 2 mainly by affecting the T max and that its effect varies with the regional climate characteristics as a function of latitudes.

Sensitivity of the regional European boreal climate to changes in surface properties resulting from structural vegetation perturbations

“…Sensible heat flux was increased going from tundra to more complex canopy vegetation, with both shrubs and trees enhancing the sensible heat flux to the atmosphere. These findings are supported by modeled findings for heat flux changes resulting from similar vegetation changes (Jeong et al, 2011(Jeong et al, , 2014Snyder and Liess, 2014). Snyder and Liess (2014) found annual mean increases in both sensible and latent heat fluxes as responses to lowered albedo and increased net radiative forcing.…”

“…Bhatt et al (2010) link increased high-latitude ecosystem productivity to a decrease in near-coastal sea ice and summer tundra surface temperatures, supporting the findings of Jeong et al (2014), who conclude that vegetationatmosphere-sea ice interaction gives rise to additional positive feedback of the Arctic amplification, based on a series of coupled vegetation-climate model simulations under a doubled CO 2 environment. In addition, the northward expansion of boreal and Arctic vegetation into previously tundracovered regions, also referred to as the Arctic greening, is a widely observed feature across the Arctic region.…”

“…For the summer months, the increased radiative flux was partitioned into sensible rather than latent heat, due to repartitioning of evaporative flux, leading to a JJA temperature increase of 0.4 K, and little or no increase in nearsurface humidity and precipitation. Jeong et al (2014) on the other hand, found increases in both latent and sensible summer season fluxes in response to Arctic greening, leading to relatively large increases in JJA near-surface temperatures (1.95 K).…”

“…Soja et al (2007) concluded that substantial observational evidence across the circumpolar boreal region over the past several decades indicates that the biosphere in the region has already responded to climate changes in accordance with modeled predictions. They found upper and lower tree lines in mountainous regions across Siberia to have altered in response to a warmer climate, as predicted by global dynamic vegetation models (e.g., Jeong et al, 2011Jeong et al, , 2014. In addition, observed changes to vegetation include increased biomass production in highlatitude ecosystems as a response to higher temperatures and longer growing season.…”

“…Several global vegetation modeling studies have predicted potential vegetation changes in response to future warming and elevated CO 2 concentrations (e.g., Lucht et al, 2006;Alo and Wang, 2008;Sitch et al, 2008;Strengers et al, 2010;Jeong et al, 2011;Jeong et al, 2014). Common features in these studies include the migration of boreal forest towards higher latitudes and altitudes (i.e., northward expansion of trees and shrubs into tundra ecosystems) and the replacement of boreal forest by more temperate vegetation species along the southern edges of the boreal zone.…”