Today's Venus is Cool: Relatively Speaking

"Hellish Venus Atmosphere May Have Had Cooling Effect"
Space.com (September 21, 2010)

"It may seem downright bizarre, but a new model of Venus' super-hot atmosphere suggests its greenhouse gases may actually be cooling the planet's interior.

"These gases initially cause Venus' temperature to rise, but at a certain threshold, they can trigger dynamic processes – which researchers call 'mobilization' – in the planet's crust that cool the mantle and overall surface temperature, researchers found...."

"...Noack and co-author Doris Breuer built a one-of-a-kind Venus computer model in which the planet's hot atmosphere was paired with a 3-D model of the interior.

"Unlike on Earth, Venus' high temperatures have a much bigger effect on the rocky surface, which ultimately loses its insulating qualities, the researchers said.

" 'It's a little bit like lifting the lid on the mantle: The interior of Venus suddenly cools very efficiently and the rate of volcanism ceases,' Noack said. 'Our model shows that after that "hot" era of volcanism, the slow-down of volcanism leads to a strong decrease of the temperatures in the atmosphere.'..."

Even today's 'cool' Venus is hot by our standards. The average surface temperature is 860 degrees Fahrenheit / 460 degrees Celsius.

The researchers' model shows that the current 'cool' Venus, with subdued volcanic activity - could still have active volcanoes in a few spots. Which is a pretty good match with what's been observed.

If the Noack - Breuer model is a fairly accurate description of how Venus has been shedding heat, this looks like a sort of feedback loop we see in our endocrine system - or the thermometer and furnace in houses.