[S25-1] Development and application of geothermal databases

[S25-1-04] Energy Budget of the Global Lands in the Course of Recent Climate Change

^○Shaopeng Huang^{1, 2} (1.Xi'an Jiaotong University, Xi'an, Shaanxi, China, 2.University of Michigan, Ann Arbor, Michigan, USA)

Ground surface temperature variation imposes transient perturbation to the steady state of the thermal field of the uppermost crustal layer, hence, impacts the energy flux across the ground surface. In this regard, continental lithosphere is an important regulator of the energy budget of global climate system. Great efforts have been devoted to detect and attribute the heat content changes of the global oceans and atmosphere. Less well understood is the extent of subsurface warming of the global lands. I examined the annual heat content change of the continental landmasses over the period from 1850 to 2015 based on meteorological records. Result shows that the rocks beneath 30% of the globe has absorbed 19 ZJ (10^21 Joules) of thermal energy since the beginning of the 20th century global climate warming, more than twice as much thermal energy as the entire atmosphere has absorbed. The calculated subsurface temperature anomalies are consistent in general with the anomalies recorded in more than 1000 borehole profiles of the global database of borehole temperatures for climate reconstruction. I further extended the analysis to Year 2100 under three climate scenarios: a business as usual scenario of continuation of the recent warming trend, a climate stabilization scenario with ground surface temperature maintaining at the current state, and an energy freeze scenario of halting the ground surface energy flux. If the observed global warming trend over the 25 year period (1991-2015) is to continue at 2.89K/100a, an additional 51 ZJ of heat will be trapped underground by the end of the 21st century. Even if the global surface temperature is to stabilize at the current state throughout the rest of the 21st century, the continental landmasses will continue to acquire over 15 ZJ extra energy from the atmosphere. An overall 0.72 K cooling at the global ground surface between 2016 and 2100 is required to avoid further heating of the continents.