Researchers Analyze Relationship between Surface Temperature and Outgoing Heat of Earth


Researchers from Massachusetts Institute of Technology (MIT) predicted breakdown of linear relationship between surface temperature and outgoing heat of Earth

The Earth sheds more heat into space as its surface warms up and the relationship between the Earth’s surface temperature and its outgoing heat is straightforward and linear. Now researchers from MIT’s Department of Earth, Atmospheric and Planetary Sciences (EAPS) explained and predicted the timescale of breakdown in this linear relationship. The findings are expected to help climate researchers to model the effects of climate change.

The EAPS team observed that the Earth emits heat to space from the surface as well as from the atmosphere. The air holds more water vapor as both the surface and atmosphere heat up, which in turn acts to trap more heat in the atmosphere. This strengthening of greenhouse effect of the Earth is known as water vapor feedback. The researchers found that the water vapor feedback is sufficient to reduce the rate at which the warmer atmosphere emits more heat into space. The team built a radiation code, which is a model of the Earth that describes heat emission or infrared radiation into space. The code simulates the Earth as a vertical column with the ground as a starting point, progress up through the atmosphere, and reaches into space. A surface temperature can be entered into the column and the code measures the amount of radiation that escapes through the entire column and into space.

The temperature knob can be turned up and down to determine the effect of different surface temperatures on the outgoing heat. The researchers plotted the data and observed a straight line that signifies a linear relationship between surface temperature and outgoing heat. Moreover, the researchers concluded that the Earth sheds more heat into space when the surface temperature gets hotter. However, the phenomenon is also coincided by water vapor builds up that absorbs and trap heat at certain wavelengths. This leads to a greenhouse effect that prevents a fraction of heat from escaping. The research was published in Proceedings of the National Academy of Sciences (PNAS) on September 24, 2018.