  The contribution of anthropogenic and natural greenhouse gases to the
atmosphere from the territory of Russia, China, USA and Canada to global
climate change under different scenarios of anthropogenic emissions in the 21st
century has been assessed. It is shown that the consideration of the changes in
climate conditions can affect the impact indicators of greenhouse gas emissions
on the climate system, especially over long time horizons. In making decisions,
it is necessary to take into account that the role of natural fluxes of
greenhouse gases into the atmosphere from the terrestrial ecosystems can
change. For all the countries considered, the uptake of CO$_2$ by terrestrial
ecosystems under all scenarios of anthropogenic impact begins to decrease in
the second half of the 21st century, so its stabilizing effect may gradually
lose importance. At the same time, methane emissions in all of the considered
regions are increasing significantly. The net effect of these greenhouse gas
natural fluxes in some cases can even lead to warming acceleration by the end
of the 21 st century.

Atmospheric and Oceanic Physics;Geophysics