Transcript János Mika, DSc

GLOBAL CLIMATE CHANGE:
THE SCIENCE BEHIND
Prof. Dr. János MIKA
Hungarian Meteorological
Service, Budapest
Martonvásár, 29 October, 2008
Outline:
• 1. Is our climate breaaly warming?
• 2. Reasons and processes
• 3. Can we predict climate at global scales?
• 4. Smooth warming vs. tipping points
• Conclusion
Forecasts and reality after 1990, (IPCC, 2007)
1. Is our global climate warming?
http://data.giss.nasa.gov/gistemp/graphs/
(Last modified: 2008-01-11)
Borehole reconstruction
http://sealevel.colorado.edu/
http://nsidc.org/data/seaice_index/images/daily_images/N_daily_extent_hires.png
Permarost area is decreasing
2. Is the warming mainly of
anthropogenic origin?
Four main ways of anthropogenic climate forcings
CLIMATE FORCING FACTORS
Greenhouse gases
Carbon-dioxide
(CO2)
Methane (CH4)
(IPCC, 2007)
Nitrious oxide
(N2O)
Variations of the „Solar Constant”
Reconstructed Solar Variability
STRATOSPHERIC
Indirect effect of
TROPOSPHERIC O3
aerosols
Aerosol concentration:
Szulfát-kibocsátás
Increase for long time, now global stagnation, with decrease in
the developed regions
Global dimming
Estimates of the terrestrial surface average value are:
5.3% (9 W/m²); over 1958–85 (Stanhill and Moreshet, 1992)
2%/decade over 1964–93 (Gilgen et al, 1998)
2.7%/decade (total 20 W/m²); up to 2000
(Stanhill and Cohen, 2001)
4% over 1961–90 (Liepert 2002)
After 1990: global brightening!
Credit: Michael Mishchenko, NASA
Geographical distribution
of the radiative forcings
(from 1750 to 2000): GGs
a) Well-mixed greenhouse gases
b) Stratospheric ozone (1979-94)
c) Tropospheric ozone increase
Geographical distribution
of the radiative forcings
(from 1750 to 2000): aerosol
g) Surface albedo due to land-use
changes (deforestation only)
h) Indirect effect by sulfate
i) Contrails (aviation)
3. Can we predict the global
future?
Development of GCMs
Maximum resolution:
1.
1991
2.
1996
3.
Golf-áram
Észak Atlanti
mélységi vizek
550 km (T21)
250 km (T42)
IPCC Reports
2001
Csak antropogén hatással együtt
reprodukálható a XX. század!
180 km (T63)
szimulált,
csak természetes
4.
2007
110 km (T106)
Mi várható a jövőben ?
A XXI.
századra
várható
melegedés
mértéke
különböző
kibocsátási
szcenáriók
esetére
(Forrás:
IPCC, 2007)
Állandó légkör mellett is: +0,5 oC. 2100-ra (1981-2000-hez képest)
Legvalószínűbb változás: 1,4 - 4,2 oC. Teljes sáv: 1,1 – 6,4 oC
Sea-level changes:
past – present – future
Northern polar sea-ice decrease (in summer!)
Mi várható a jövőben ?
2080-2099-re vonatkozó relatív változások a
felhőborítottságban
1980-1999-hez viszonyítva
(Forrás: IPCC, 2007)
Changes in Europe in averge of 20 GCMs
(2080-2099 vs. 1980-1999)
Winter
Precipitation
Temperature
Annual
(IPCC, 2007)
Summer
4. Smooth warming, or tipping
points?
Why and how to mitigate the warming?
Potential catastrophic tipping points
1786–1793 PNAS February 12, 2008 vol. 105 no. 6
www.pnas.orgcgidoi10.1073pnas.0705414105
(+ 8 other changes in dierent regions)
(Tipping-points)
Global ocean circulation
Cooling
Warm
surface
current
Intermediate
waters
Warm and less saline
Antarctic circumpolar current
A simplified view of the global thermohaline
conveyor belt, showing cooling and
downwelling in the North Atlantic.
Weakening of the Atlantic
„conveyor belt”) in 9 models
(IPCC TAR, 2001> Figure 9.21)
Mean: 10-30 Sv = 10-30 million cubic meters/sec
Wood et al., 2003
Not an „ice age”, at all!
Do we have a chance to limit the
warming?
Energy costs
Good example of CFC-11
ATTITUDES CONCERNING THE
ENVIRONMENT (the 1st is false!)
Conclusions (IPCC, 2007 WG-I, selected):
• Most of the observed increase in global average
temperatures since the mid-20th century is very likely
(90 %) due to the observed increase in anthropogenic
greenhouse gas concentrations. This is an advance
since the TAR’s conclusion that “most of the observed
warming over the last 50 years is likely (67 %)to have
been due to the increase in greenhouse gas
concentrations”.
• …it is extremely unlikely (<5 %) that global climate
change of the past 50 years can be explained without
external forcing, and very likely (90 %) that it is not
due to known natural causes alone.
Conclusions (cont.):
• The equilibrium climate sensitivity is likely (67 %) to be in
the range 2°C to 4.5°C with a best estimate of about 3°C,
and is very unlikely (<10 %) to be less than 1.5°C. Values
substantially higher than 4.5°C cannot be excluded, but
agreement of models with observations is not as good for
those values.
• Based on current model simulations, it is very likely (90 %)
that the meridional overturning circulation (MOC) of the
Atlantic Ocean will slow down during the 21st century.
However, it is very unlikely (<10 %) that the MOC will
undergo a large abrupt transition during the 21st century.
Longer-term changes in the MOC cannot be assessed with
confidence.
Thank you or your kind attention!
[email protected]