Risk analysis of global warming-induced greenhouse gas emissions from natural sources

Abstract

The increase in the emissions of greenhouse gases (GHG) CO2, CH4, and N2O is the most important factor causing global warming. Natural sources make up about 96%, 46%, and 64% of total emissions of the three gases, respectively. Relatively small man-made CO2 fluxes, together with CH4 and N2O (with a radiative force 34 and 298 times higher than that of CO2, respectively) upset the natural balance of the carbon (C) cycle and create an artificial forcing of global temperatures which is warming the planet. However, even after stopping all anthropogenic CO2 emissions, the warming-induced GHG from natural sources will cause an on-going temperature increase and many resulting environmental problems. Based on literature, we analyse the potential change in GHG emissions from the main natural sources, which are influenced by the effects of global warming. Since there are various uncertainties in the estimations of terrestrial-atmosphere and ocean-atmosphere CO2 exchange, this most important factor remains un-predicted and needs significantly more investigation of the ability of oceans and terrestrial ecosystems to absorb CO2. Both CH4 and N2O emissions may continue to increase. The thawing of CH4 hydrates in the ocean shelf and in permafrost regions is the largest long-term threat for global warming, but even now rising temperature will enhance emissions from wetlands, lakes, vegetation and even upland soils, due to an increasing threat of wildfires. Changes in hydrological regime are the main driving force for N2O emissions.