Date post: | 07-Aug-2015 |
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Climate Change: Urgency in Slow Motion
Bart Verheggen, PhD Amsterdam University College
Climate Communication & Consultancy http://KlimaatVerandering.wordpress.com/ http://OurChangingClimate.wordpress.com/
@KlimaatVeranda @BVerheggen
The scientific position
“studies from diverse sources indicate a consensus that climate changes will result from man’s combustion of fossil fuels and changes in land use.”
National Academy of Sciences Archives, An Evaluation of the Evidence
for CO2-Induced Climate Change, 1979
IPCC was established in 1988 in response to scientific predictions
has hardly changed since 3 decades…
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Arrhenius, Fourier, Tyndall, …
Scientific process
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• Science is based on critically evaluating available evidence in the context of existing knowledge
• If more knowledge confirms the existing theory • This leads to a growing consensus amongst
scientists about the big picture
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Greenhouse effect
Greenhouse gases absorb infrared radiation
Less energy escapes to space
Earth is warmer than it would otherwise be
Human activity has increased the concentration of greenhouse gases
Earth retains more energy and heats up as a result
Observations (from space and from earth’s surface) confirm the enhanced
greenhouse effect
Bart Verheggen
http://svs.gsfc.nasa.gov/vis/a000000/a004000/a004030/
Global warming since 1880 (5 year running mean)
Climate has always changed
Process • Plate tectonics • Orbital variations • Carbon cycle • Sun • Volcanoes • El Niño / La Niña
• Man-made GHG & aerosols
Timescale (years) > 1,000,000 > 10,000 (ice ages) 1000 – 1,000,000 variable 1-3 1-2 variable
Solar output varied strongly past 400 years
Little Ice Age
But no trend since 1950’s
• No trend in the sun (or cosmic rays) since 50 years
• Nights have warmed more than days • Stratosphere has cooled • Enhanced greenhouse effect observed from
space and from the ground
Inconsistent with dominant solar influence
Sun or Greenhouse Gases?
• No trend in the sun (or cosmic rays) since 50 years
• Nights have warmed more than days • Stratosphere has cooled • Enhanced greenhouse effect observed from
space and from the ground
“fingerprint” of enhanced greenhouse effect
Sun or Greenhouse Gases?
Projections of future climate change
If global emissions peak within next few years then decline
Ongoing increases in global greenhouse gas emissions
Emissions cuts make little difference for next few decades (inertia)
Expected warming in the future depends on: - total emissions (e.g. red or blue trajectory) - climate system response (uncertainty band)
Con
cent
ratio
n (p
pm)
Year
Em
issi
on (G
ton
/ yea
r)
emission
concentration
Decreasing the CO2 concentration takes much longer than
increasing it
Climate responds very slowly to emission reduction
• Oceans act as heat buffer • Long response time of CO2
– Increasing CO2 goes faster than decreasing CO2 – Climate warming goes faster than climate cooling
• Sea level responds even slower than temperature
Urgent?
• Warming is delayed
• Cooling will be delayed much more so
• Thus early action is needed (*)
(*) assuming we value having a relatively stable climate
• Direction of changes is clear
- Earth is warming up
- It’s due to us
• Uncertainty about speed
• Delayed response
“if you jump out of an airplane you need a crude parachute more than an accurate altimeter” (Herman Daly)
Conclusions
“What’s the use of having developed a science well enough to make predictions if, in the end, all we’re willing to do is stand around and wait for them to come true?”
Sherwood Rowland
Thank you!
http://KlimaatVerandering.wordpress.com/ http://OurChangingClimate.wordpress.com/
@KlimaatVeranda @BVerheggen