It is obvious first of all, since the temp of Venus is NOT primarily due to it being closer to the sun.
But obviously global warming has positive feedback mechanisms that have to lead to a race condition, if allowed.
In particular, the hotter the planet gets, the more moisture evaporates into the atmosphere, and that then greatly increases the heat retention.
There is no way to stop the Earth from becoming the temperature of molten lead if we get to the point the temperature gets high enough to start enough water vapor evaporating.
As the Earth heats up more water will make its way into the atmosphere, trapping even heat near the surface. To predict how much temperatures could rise in the future, scientists are working to understand how much water could enter the atmosphere and how that might contribute to climate change.
earthobservatory.nasa.gov
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Will Runaway Water Warm the World?
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Across the globe, temperatures are slowly creeping up. According to the U.S. National Climatic Data Center, the global average surface temperature has gone up 0.4 degrees Celsius (plus or minus 0.1 degree) in the past 25 years alone. While the extra heat may not have you sweating yet, larger increases are predicted, and that has some people tugging at their collars. The Intergovernmental Panel on Climate Change, a policy advisory group made up of members of the World Meteorological Organization and the United Nations Environment Programme, estimates that the average global surface temperature could climb anywhere from 1.4 to 5.8 degrees Celsius by the year 2100.
Part of the reason the predicted temperature range is so great is that scientists don’t entirely understand whether the atmosphere will become more humid as it warms, and humidity is one of the primary factors that will influence how much the climate will warm over the next century. If the humidity of the atmosphere does indeed increase, it can as much as double the warming from carbon dioxide alone. Thus, an understanding of how the humidity of the atmosphere will change is of fundamental importance in predicting future climate. The problem is one that Ken Minschwaner and Andrew Dessler, researchers at NASA Goddard Space Flight Center, have worked to remedy using data from the Upper Atmosphere Research Satellite (UARS).
Minschwaner, also a Professor of Physics at the New Mexico Institute of Mining and Technology, and Dessler, also a researcher with the University of Maryland’s Earth System Science Interdisciplinary Center, formulated a simple, one-dimensional model to describe how the humidity of the atmosphere will change as the Earth heats up in response to carbon dioxide emissions from burning of fossil fuels. Surprisingly, their model predicted smaller increases in humidity in the upper atmosphere than large global climate models do, and data collected by the Microwave Limb Sounder and the Halogen Occultation Experiment on NASA’s UARS satellite support their model. Their findings imply that the Earth will warm significantly, but probably not as much as most global climate models predict. Their results appeared in the Journal of Climate on March 15, 2004.
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Predictions of warming in the next 100 years vary by about 5 degrees Celsius, from a low of 1.4 degrees to a high of 5.6 degrees. The wide variation is due in part to uncertainty in the magnitude of the feedback between warming and increased rates of evaporation. In this graph, dark green areas represent predictions based on the averaged results of multiple climate models, while light green areas represent the predictions of single climate models.
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As the Earth heats up more water will make its way into the atmosphere, trapping even heat near the surface. To predict how much temperatures could rise in the future, scientists are working to understand how much water could enter the atmosphere and how that might contribute to climate change.
earthobservatory.nasa.gov
coralglass.media
www.nature.com
