Presentation of Bart Verheggen (Amsterdam University College) on 'Climate change: urgency in slow motion' during the conference 'Environmental challenges & Climate change opportunities' organised by Flanders Environment Agency (VMM)

1. 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

2. 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…
Dddd
Arrhenius, Fourier, Tyndall, …

3. Scientific process
fffffffffffffffffffffffff
• 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
fffffffffffffffffffffffff

4. 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

5. http://svs.gsfc.nasa.gov/vis/a000000/a004000/a004030/
Global warming since 1880 (5 year running mean)

7. Long term trend vs short term variability
f
http://sks.to/escalator
;

8. The increase in Earth’s
total heat content
is dominated by the
ocean
3/24/2015 Bart Verheggen 8

9. 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

10. Solar output varied strongly past 400 years
Little Ice Age
But no trend since 1950’s

11. • 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?

12. • 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?

13. 3/24/2015 14
Bart Verheggen
Observations
in black
Model simulations
in color

14. 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)

15. Concentration(ppm)
Year
Emission(Gton/year)
emission
concentration
Decreasing
the CO2 concentration takes much longer than
increasing it

16. Long term sea level rise
Sealevelrise(metres)

17. 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

18. Climate responds very slowly
to emission reduction

19. Urgent?
• Warming is delayed
• Cooling will be delayed much more so
• Thus early action is needed (*)
(*) assuming we value having a relatively stable climate

20. • 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

21. “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