Thread: Does global warming cause oceans to evaporate?

I'm familiar with the prediction that global warming is melting the polar ice caps and glaciers around the world causing the oceans to rise. But wouldn't global warming also cause the oceans to evaporate by a certain degree, thereby off setting the rise in ocean levels? When scientists make predictions about how much ocean levels will rise, do they take into account rates of evaporation?

Believe it or not a significant part of the the rise in sea levels isn't the amount of water in them but rather the thermal expansion of the water already there. Like anything else the hotter water gets the more room it takes up.

Of course, global warming causes the oceans to evaporate by a certain degree and offset the rise in ocean levels but it has many factors such as the rate of ice melt, the amount of ice loss from the ice sheets, and the rate of thermal expansion. The amount of water evaporated from the ocean is relatively small compared to the amount of water added to the ocean from the melting of ice sheets and glaciers. Nonetheless, it is projected that the sea level will continue to rise in the future.

Originally Posted by gib65

I'm familiar with the prediction that global warming is melting the polar ice caps and glaciers around the world causing the oceans to rise. But wouldn't global warming also cause the oceans to evaporate by a certain degree, thereby off setting the rise in ocean levels? When scientists make predictions about how much ocean levels will rise, do they take into account rates of evaporation?

There has to be a permanent increase in atmospheric water content - it is evaporation minus precipitation, not evaporation alone.

An increase in atmospheric water vapor content is happening - but it is about 1.3% per decade or sea level equivalent of 0.45mm per decade or 0.045mm per year. (by my rough calculations). That makes the "off setting" less than 1% of the current sea level rise. The most significant effect of more water vapor in the atmosphere isn't reducing sea level rise it is amplifying global warming; water vapor is a greenhouse gas and water vapor feedback, more water vapor because warmer air holds more water vapor, effectively amplifies warming from CO2 and methane by two to three times, or global warming wouldn't be nearly as alarming as it is.

Current global sea level is rising at around 5mm per year and the total amount of water in the atmosphere is equivalent to about 25mm of liquid water over the whole planet or about 35mm of ocean level; if water vapor in the atmosphere doubled it would compensate for about 7 years worth of sea level rise - and greatly increase global warming and the rate of sea level rise.