Transcript Climate change - is it really happening

Climate Change – is it really happening?
Kathy Maskell and Maria Noguer
Walker Institute for Climate System Research,
University of Reading
Overview
• MYTH 1: Recent changes are nothing unusual
• MYTH 2: People are not to blame
• MYTH 3: We can’t believe forecasts of climate
• MYTH 4: Maybe a bit of warming wouldn’t be so bad!
• MYTH 5: We’re doomed – there’s nothing we can do
MYTH 1: Recent changes are nothing
unusual – climate has always varied
Recent warming is unusual
The northern hemisphere is probably the warmest it’s been
for at least 1000 years
Temperature can be
inferred from tree ring
width
Mann et al., Science 1999 (Northern Hemisphere only)
FACT 1: Something unusual is happening to
our climate
• The land, oceans and the air are all warming, sea ice
and glaciers are melting
Mountain
2004
1941
glaciers
are melting
Sub-Saharan Africa and
Mediterranean are getting drier
Northern Europe
is getting wetter
MYTH 2: People are not to blame
Variation’s in the Sun’s output
Volcanoes
People are changing the atmosphere in drastic ways
Carbon dioxide levels are higher than at any time in last
650,000 years!
The Greenhouse Effect
The natural greenhouse effect – without it temperature
would be -15oC - brrr
Burning fossil fuels is adding to the natural greenhouse
effect
enhanced
a warmer world
greenhouse effect
..most escapes to outer space
and cools the earth...
SUN
More CO2 traps more
IR, thus reducing the
cooling further
Most sunlight
passes
through the
atmosphere..
..and warms the earth.
CO2
CO2
Infra-red radiation
is given off by the earth...
The Climate System
Climate models must contain the atmosphere, the
oceans, ice and the land surface and consider all the
possible influences on climate
Climate models are our laboratory.
We use them to understand past changes and to
predict the future.
The earth is represented by a
grid of squares, typically of
length 250 km, and by a stack
of layers.
This gives us a 3-D picture of
the circulation of the
atmosphere and oceans
FACT 2: People are warming the Earth
MYTH 3: We can’t forecast climate 100
years into the future.
How do we forecast climate?
Future greenhouse
gas/aerosol emissions depend on population, energy
use, new technologies, etc
Climate forcing
Climate system
response - clouds, ice,
oceans etc
Emissions of CO2 through the 21st century
But why should we trust climate models?
• Physically based – incorporate huge amount of
research into climate processes
• Models can simulate current and past climate
• Even without using climate models there are
sound physical reasons why increasing GHGs will
cause warming
Climate models have their limitations:
• Less confidence in regional/local and extremes
• Less confidence in rainfall than temperature
FACT 3: Climate change will get worse in the
21st Century
By 2100: world could be 2 to 4oC warmer – on top of the
0.7oC we’ve already seen.
IPCC (2001)
MYTH 4: Maybe warming wouldn’t be so bad!
Climate change –
bring it on!
What about the UK?
Remember lower confidence at regional/local
scales:
More hot/dry summers likely - nice on the beach,
not so nice in the city
More winter flooding
Sea level rise
More storms??
Sea level rise
Sea level could rise by around 0.5m by 2100
Millions more people at risk of flooding
Change from the present day to the 2080s
UK Climate
Impacts
Programme
Food
Impacts on food
Percentage change in
average crop yields
for staple crops:
wheat, maize and rice.
2020’s
Yellow, brown and red
areas denote lower
yields
2050’s
But note increased
yields in some
northern latitudes due
to more favourable
climate
2080’s
% change
-40
+40
FACT 4: We know there is a risk of serious
impacts from climate change
MYTH 5: We’re all doomed –
there’s nothing we can do!
FACT 5: We can deal with climate change if
we do something now
Coping with the climate
change we can’t
avoid
Reducing emissions to stop
climate change getting too
bad
CLIMATE CHANGE IS HAPPENING…….
…..AND ITS EFFECTS ARE LIKELY TO BE VERY PROFOUND