Human and the Earth

ASTR 1420

Lecture 26

Section 10.5

Global Warming

Doesn’t everyone already know about Global Warming?

GALLUP anual poll

global warming is generally exaggerated?

43

GALLUP poll

When the effects of global warming will begin to happen?

GALLUP poll

The main cause of global warming?

394.45 now!

Consequences

Rising sea level130

2010

Past history of CO2 and Global Average Temperature

Venus and Earth

Venus• 0.7 Astronomical Unit• 0.95 Rearth

• Rocky planet• Geological activity• Thick atmosphere

• 900°F200,000 more CO2 in atmo

Earth• 1.0 Astronomical Unit (AU)• 1.0 Rearth

• Rocky planet• Geological activity• Thick atmosphere

• 57°F

Why so much more CO2 in the Venusian atmosphere?

Total content of Carbon (CO2) inVenus and Earth are same.

CO2 in the Earth : atmosphere 1, ocean 60, rocks 170,000

CO2 in the Venus: atmosphere ~200,000, ocean 0, rocks 0

If Venus and Earth were formed similarly, shouldn’t they have nearly the same atmospheric CO2 content?

Venus was like a tropical paradise (~80°F) before

Dry effect

Temp was high enough initially so that there was no water condensation

no CO2 dissolutionaccumulated outgassed CO2

warmer tempmore evaporation of waterH2O broken by solar UVhigher CO2 and hotter temp

Wet effect

More net evaporation than precipitation

ocean gradually vanishedhigher T caused rocks to release

stored carbonmore H2O in the atmosphere

causing even stronger greenhouseH2O broken by solar UVdry, barren, hot planet

Either through “Dry” or “Wet” runaway greenhouse effect, Venus lost all her water and CO2 had to be remained in the atmosphere

Regulation of Earth’s Climate

• The CO2 cycle acts as a thermostat• For the warm Earth, carbonate minerals forms in the oceans at a more

rapid rate, and takes away more CO2

What global warming? We don’t need to worry about it since the CO2 cycle will take care of it!!

The cycle is about 400,000 years, and this is a very delicate process

Can Earth follow the same footsteps of Venus?

YES!

• “Wet” runaway greenhouse effect on Earth would require that the majority of the oceans around the world would evaporate more water than precipitate critical temperature is about 80F

• By 2100, average global temperature can rise ~70F which is dangerously close to the critical point.

• The only thing that has prevented Earth from being another Venus was the CO2 cycle which is a slow, yet very delicate process.

• If this process were ever to start, there is not way to stop it

Localized Runaway Greenhouse effect• Pacific ocean to the NE of Australia exhibited a runaway effect (May 2002)

• This location was warm enough year round to continually evaporate more water vapor than precipitated back to it.

• Luckily, this is only a localized effect and surrounding ocean compensate for it. But, this may be an example tells us that we are uncomfortably close to the entire planetary runaway effect.

Should we take a risk with the tipping point?

Dr. Martin Luther King, Jr.

"Unlike the plagues of the dark ages or contemporary diseases we do not yet understand, the modern plague of overpopulation is soluble by means we have discovered and with resources we possess. What is lacking is not sufficient knowledge of the solution, but universal consciousness of the gravity of the problem and the education of the billions who are its victims.”

Acceptance Speech: Margaret Sanger Award in Human Rights, 1966

As scientists and citizens, we have responsibilities to remind the public.