Theme 9 – Venus and Global Warming

ASTR 101Prof. Dave Hanes

Enigmatic Venusa near-twin of Earth in size and mass

Cloud-covered, hard to study. Imagination run riot!

Goddess of Beauty? Or Hellish Reality?

Hot Enough to Melt Lead

Other Unpleasant FeaturesThe atmosphere is 96% CO2.

The clouds consist of sulphuric acid droplets; there is acid rain.

The air pressure at the surface is ~90 x Earth’s. This is like being 1 km deep in the ocean.

(American Seawolf submarines have an estimated ‘crush depth ’ limit of about 750 metres)

Runaway Greenhouse Effect

It is NOT the clouds of Venus but rather the thick CO2

atmosphere that has led to the runaway greenhouse effect.

Indeed, the clouds reflect a lot of sunlight (so Venus is very bright!). The clouds actually reduce the amount of incoming radiation. Without them, it would be even hotter.

One Surprising Feature

The surface of Venus is the same temperature everywhere, even though it rotates very slowly (and backwards, too, as it happens). You might expect the side facing the Sun to be hot, the other side relatively cool.

By contrast: on Earth, consider how the soil temperature changes over the course of a day:

Why is Venus’s Heat So Uniform?

There are tremendously high winds in the Venusian atmosphere that serve to redistribute the heat (but no oceans to do the same).

Runaway Greenhouse Effect- a Timely Warning for Earth

Venus is hot because of the extreme greenhouse warming caused by the thick CO2 atmosphere.

The Earth has just as much CO2 as Venus does…

So are we likewise threatened?

NO. Most of the CO2 on the Earth is tied up in carbonate rocks (formed via geochemistry, or from life-forms – sea shells, etc). There is also some in the form of vegetation, or dissolved in the oceans.

A Complex Cycle

Atmospheric CO2 is Increasing

- and the global temperature as well

Is Nature to Blame?

http://www.youtube.com/watch?v=bgRnVhbfIKQ

Know the Numbers!

“I have flown twice over Mt Saint Helens out on our west coast. I’m not a scientist and I don’t know the figures, but I have a suspicion that that one little mountain has probably released more sulphur dioxide into the atmosphere than has been released in the last ten years of automobile driving…..”

President Ronald Reagan

Human Activity

1. Increased release of CO2 (especially from fossil fuels).

2. Clearing of rain forests, etc.

Other Threats

Global warming will lead to the melting of frozen tundra, where rotting vegetation will release lots of methane (CH4) – a more potent greenhouse gas than CO2 itself.

Predictable Outcomes

a warmer atmosphere: more energy content, leading to more extreme weather events, less predictable and more unstable climate

melting ice caps (Greenland, Antarctica) lead to sea-level rise, flooding of coastal areas

warmer oceans also lead to sea-level rise (the water expands with temperature)

change in global weather patterns may lead to extreme heat, drought and desertification in many areas (e.g. Australia)

reduced habitats for polar bears, coral reefs, …

Sea Level Change

A Terrifying Sequence

https://www.youtube.com/watch?v=hC3VTgIPoGU

Mediating Factors

1. A rise in temperature would evaporate more water in the atmosphere, yielding more clouds. They would reflect more light (remember Venus?) and might serve to moderate the growing greenhouse effect.

Conversely

2. Suppose the sun dimmed for some reason. Perhaps the biosphere would respond by producing more dark-coloured plants, extensive algae on the surfaces of ponds and the oceans, etc, to absorb more light and keep the biosphere temperature higher.

How Would the Earth ‘Know’ to Do These Things? GAIA

This hypothesis has elements of mysticism around it – almost suggesting a sentient Earth. But there may be some validity to certain elements of it in a natural-feedback way. In its most developed form, it is known as the GAIA Hypothesis, championed by James Lovelock and Lynn Margulis.

http://www.scienceclarified.com/Ex-Ga/Gaia-Hypothesis.html

A Continuing Concern

Climate change is a hot topic that is as much political and economic as it is scientific.

I personally believe that the problem is real, serious, and a consequence of human action.

It would be irresponsible to count on the Earth itself ‘coming to our rescue’ by putting our entire trust in GAIA!