1. 7/29/09
Heat in, Heat Out Too cold
• If all the heat coming in went out the average
temperature on the Earth’s surface would be
‐19
How?
• Some molecules absorb the heat coming up
from the earth,
• They then reemit in in random direcFons –
50% of it comes back.
Some of the gases that do this are
And it is:
increasing – a lot!
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2. 7/29/09
So? It might make Canberra’s winter
more bearable…
• But we are already seeing increases in:
– Floods
– Droughts
– Cyclones Ice is melFng
• In some places the monsoon are failing
• Some diseases are more widespread
• Salt is intruding into groundwater
And
Understand the Size Understand the Scale of the Challenges
of the Challenges Satellite Image early Marc
h 2000
Measure
it 2
11,000 km
295 km
km
37
Iceberg B15 calving from The Edg
the Ross Ice Shelf e of B15
A
Go in for a closer look Iceberg Alley
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3. 7/29/09
Sea levels do change
• During the last ice age (20,000 years ago) sea
levels were about 120m lower.
• 14,000 years ago sea levels rose 20m in just
400 years as some major ice sheets melted.
But when they wrote the report you • Current sea levels have been remarkably
have been asked to read, no one stable since about 3000 years ago
thought this would happen • about the Fme humans started building things, mostly
by the sea.
Greenland and AntarcFca So what might this look like:
• Greenland is now clearly melFng much faster • hZp://flood.firetree.net
than previously thought. AntarcFca probably is
too.
• Each could raise sea levels by 5m, that’s 10m
in total. And it could happen within this
century.
Will Steffen @ ANU
What we are risking at a 2 degree rise:
says things can change in a hurry:
…the rapid disintegraFon of the large ice sheets • Sea levels
on Greenland and AntarFca or large scale and
uncontrollable feedbacks in the carbon cycle: • 15‐40% plant and animal species
acFvaFon of the methane clathrates [frozen • Ocean acidificaFon
water and methane] buried under sediments in
the ocean floor, the rapid loss of methane from • Widespread drought and deserFficaFon
warmer and drier tundra ecosystems, increasing • Increasing heatwaves
wildfires in the boreal and tropical zones, the • Monsoon failure
conversion of the Amozon rainforest to savannah,
the release of carbon dioxide from warming • Glacial water supply – Asia and South America
soils… • Loss of major agricultural lands
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