Answer:
A. Increase in permafrost thickness
Explanation:
<u>Climate warming (like of 4°C) would increase the active layer thickness (ALT) of permafrost</u>, which can cause changes in the hydrological cycle, ecological processes, and carbon flux in cold regions.
Global warming is the long-term heating of Earth's climate system observed since the pre-industrial period (between 1850 and 1900) due to human activities, primarily fossil fuel burning, which increases heat-trapping greenhouse gas levels in Earth's atmosphere