Climate Climate
change Change
- is it serious?
– its causes and potential implications
KJM3700
1.
2.
3.
4.
5.
6.
Intro
The greenhouse effect
Emissions and concentrations
Modelling climate change
Impacts of global warming
Solutions?
Atmospheric CO2 concentrations
Energy content changes in different components of the Earth system
Blue: 1961-2003
Burgundy: 1993-2003
Increased global temperature the last 150 years
Top 11 Warmest Years On Record
Have All Been In Last 13 Years
Source: IPCC 2007
Global mean surface temperature for 2007 is
estimated at 0.41°C above the 1961-1990 annual
average of 14.00°C
Observed changes in (a) global average surface temperature, (b) global
average sea level from tide gauge (blue) and satellite (red) data and (c)
Northern Hemisphere snow cover for March-April (vs 1961-1990)
Temperature anomaly (°C) for the first half decade of the 21st century
relative to 1951-1980
(Hansen, J. 2006. Proceedings of the National Academy of Sciences)
The Arctic the
last 100 yr:
DT twice the
global mean
January 2010: The warmest January since measurements started
- globally
1. The greenhouse effect
Absorption of long-wave radiation by GHG
• H2O, clouds
• CO2, CH4,
N2O, CFC
• O3
• Scattering and
absorption of
solar radiation
by particles
and clouds
The radiation spectrum of the earth
- as seen from a satellite
Important absorption bands for GHGs
are shown above the spectrum.
Contributions to total greenhouse effect
H2O
45 – 55 %
Clouds
CO2
CH4
N2O
20 – 25%
20 – 25%
1 – 2%
< 1%
H2O
Clouds
CO2
CH4
N2O
Other
However, CO2 dominates the enhanced greenhouse effect
Radiative forcing (strålingspådriv)
A change in the radiative energy available (often given
for the ‘top of atmosphere’)
• For the well mixed (longlived) greenhouse gases the
RF is the same for all
locations
• For short-lived greenhouse
gases and aerosols the RF
varies geographically and is
higher close to the
emissions (NB: can be
negative)
Figure SPM.2
Volcanic aerosols not included (episodic)
LOSU:
Level of
scientific
understanding
IPCC, 2007.
Positive and negative feedback mechanisms act
to amplify or reduce global warming
•
•
Examples of positive feedbacks:
– Rising temperatures lead to
decreased snow and ice cover,
revealing darker ground
underneath, resulting in more
absorption of sunlight (reduced
albedo)
– Levels of water vapor, methane,
and carbon dioxide can rise in
response to a warming trend,
thereby accelerating that trend
Examples of negative feedbacks:
– A warmer atmosphere will contain
more moisture, which may result
in more clouds. Clouds (esp. low)
reflect sunlight and counteract
warming
Feedbacks in the climate system
IPCC 2007
Solar activity also affects global warming
• The sun has had a rather great effect
earlier, but it is the humans that now
are contributing to the enhanced
warming.
– Eigil Friis-Christensen, one
of the authors of an article
in Science in 1991 that
initiated a heated debate
about the importance of
changes in solar activity
• There is no apparent co-variation
between solar activity and recent
global warming
Change in solar activity is not likely to be the main cause of
the rapid increase in global temperature the last 35 years.
2. Emissions, their fate, and resulting
concentrations
Fossil fuel combustion
8000
Million metric tonnes of carbon
7000
6000
coal
oil
gas
cement prod
5000
4000
3000
2000
1000
0
1800
1850
1900
Year
1950
2000
Annual global emissions of CO2 from combustion of fossil
fuels and land-use change1850-2002
• New study indicate
that the contribution
to global CO2
emissions from
deforestation and
forest degradation is
around 12% and not
around 20% as IPCC
earlier have concluded
(van der Werf in Nature
Geoscience 2009)
Global emissions of greenhouse gases
in 2004 (IPCC 2007)
As share of CO2-eq/yr
Rapid growth in Chinese CO2 emissions (No
1 in total CO2, no 66 in CO2/cap)
Kt C
Some developing countries are projected to have a
very high growth rate
Key characteristics
of some important greenhouse gases
CO2
CH4
N2O
CFC-11
unit
ppm
ppb
ppb
ppt
Pre-industrial concentration
280
715
270
0
Concentration in 2005
380
1774
319
251
Conc. change since 1998
+13
+11*
+5
-13
5-200
12
114
45
1
25
298
-1680 - +3600
Adjustment time (yr)
Global warming pot. (GWP)
* Decreasing growth in recent years
(IPCC, 2001, 2007)
Adjustment time / response time
(Justeringstid)
• The time until the concentration increase from a CO2– puls
is reduced to 1/e (1/2.72) of the initial value
– Since CO2 is removed by several processes, first fairly rapidly
then slower, one cannot give one value.
– IPCC gives 5-200 years for CO2
– The adjustment time is important when estimating CO2
concentrations for future emission scenarios
• It has caused considerable confusion that the term lifetime (levetid) is
sometimes used for turnover time, sometimes for adjustment time
Turnover time (Oppholdstid/omsetningstid)
• The average time any CO2 molecule
stays in the atmosphere
– The turnover time is obtained
by dividing the reservoir with the flux
• Thus 750 GtC/155 GtC/yr] = 4.8 years
• Approximately the same value is obtained by measurement of
how fast 14C has been removed from the atmosphere.
The turnover time (4,8 yrs) is different from the
adjustment time (5-200 yrs)
• Because a large part of the CO2 flux is returned
to the atmosphere
• Adjustment time of CO2 in the atmosphere is determined by
the rate of removal of carbon from the surface layer of the oceans into
its deeper layers.
CO2
*CO2
*CO2
CO2
CO2
CO2
CO2
*CO2
CO2
CO2
CO2
CO2
CO2
*CO2
CO2
CO2
*CO2
CO2
CO2
CO2
*CO2
*CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
CO2
Atmosphere
CO2
Land/Ocean
The global carbon cycle –sources and sinks
• Annual
increase:
7.2+1.5+20
-2.4-22.2
=4.1 GtC
Black arrows/figures: Pre-industrial Red arrows/figures: Anthopogenic since pre-ind.
28
CO2 budgets
GtC/yr
Emissions (fossil fuel,
1980s
5.4 0.3
1990s
6.4  0.3
Net oceanatmosphere flux
Net land-atmosphere
flux
-1.8 0.8
 2.2  0.4
 2.2  0.5
-0.30,9
 1.0  0.6
-0.90.6
SUM:
Atmospheric
increase
3.3 0.1
3.2  0.1
4.1 0.1
2000-2005
7.0 0.3
cement)
Positive values are net fluxes to the atmosphere,
Negative values are net loss from the atmosphere
IPCC, 2007
Man-made carbon emissions are minor compared to
fluxes between atmosphere and land/ocean
• Man-made emissions
(7 GtC/yr) and net addition to
atmospheric pool (4.1 Gt/yr) are small
compared to the pools and fluxes
• However, it is still
of great importance
• Mr. Micawber in
Charles Dickens’
David Copperfield:
154 GtC/år
– Annual income twenty pounds,
annual expenditure nineteen and six,
result happiness.
– Annual income twenty pounds,
annual expenditure twenty pounds ought and six,
result misery.
Atmosphere
750 GtC
157 GtC/år
Land, ocean
Net ocean-atmosphere flux
• The pool of dissolved inorganic carbon (DIC) in the oceans
is about 50 times greater than the amount of carbon in the atmosphere.
– The concentration of DIC in oceans increases markedly below about
300m.
• The solubility pump
– Sinking cold, dense water in the North Atlantic and in the Southern
Ocean has high CO2 concentrations.
– The solubility of CO2 in water decreases with higher temperature,
lower pH and salinity
• The biological pump
– Phytoplankton photosynthesis lowers the concentration of CO2 in the
upper ocean and thereby promotes the absorption of CO2 from the
atmosphere
– About 25 % of the carbon fixed in the upper layer sinks into the
interior where it is oxidized releasing CO2
Net land-atmosphere flux
• Large uncertainty in estimates of
net primary production
– I.e. the balance between
photosynthesis (uptake) and
respiration (emission)
• Special events such as
storms or forest fires
produce large CO2 emissions
that are particularly difficult to measure
• Conflicting results are often found
in the literature
• How the vegetation reacts
to changed climate, may have large
effects on future climate (feedback)
The natural land (vegetaion) and ocean sinks of
CO2 1960-2005 (share of CO2)
Land
Ocean
Canadell et al. 2007, PNAS
Changes in
concentrations
• Change in CO2 , CH4, and N2O
concentrations from ice cores
and modern observations
(IPCC, 2007)
• Measurements based on ice
cores (different colours for
different studies) and
atmospheric samples (red
lines). The corresponding
radiative forcings are shown
on the right hand axes of the
large panels.
3. Modeling climate change
• To estimate future climate it is necessary to use models
– Uncertainties are substantial (clouds, ocean currents, biosphere)
although they have decreased in recent years
– Feedbacks (tilbakekoplinger) are important and often difficult to model
– The models must reproduce earlier climate reasonably well (Hindcasts)
• The models are used for various emission scenarios
• Climate sensitivity: Increase in temperature for a doubling of the
atmospheric CO2 concentration.
– IPCC uses a range 2.0 – 4.5 °C (considerably higher values can not be
excluded).
Most probable value is around 3 °C
‘All models are wrong, but some models are useful’
Svante Arrhenius
Arrhenius’ estimated that a
doubling of the CO2 concentration
would increase the global
temperature by
5 – 6 °C (climate sensitivity).
Most modern estimates are
somewhat lower, 2.0 – 4.5 °.
How to predict the future climate?
IPCC’s emission scenarios
CO2
SO2
Most used:B1, A1B and A2
I.e.: SRES reference scenarios up until 2100.
SRES: Special Report on Emission Scenarios (IPCC)
5
Actual antropogenic CO2-emissions compared to the IPCC emission
scenarios (Raupach et al. 2007, PNAS; Canadell et al. 2007, PNAS)
0
Recent emissions
1850
1900
1950
2000
2050
2100
CO2 Emissions (GtC y-1)
10
9
8
7
Actual emissions: CDIAC
Actual emissions: EIA
450ppm stabilisation
650ppm stabilisation
A1FI
A1B
A1T
A2
B1
B2
2008
2006
2005
6
5
1990
1995
2000
2005
2010
Comparison of observed temperature (black line) with a range of model
calculations without (blue) and with (red) anthropogenic forcings
(Solar flux and volcanoes)
IPCC 2007: DT 1.1 – 6.4 °C within 2100
Emissions at
2000 level
T scenarios for 2030 and 2100
Projected surface temperature changes for the early and late 21st century relative to the
period 1980–1999 (IPCC, 2007)
4. Impacts of global warming
IPCC 2007: DSLR 18 – 59 cm within 2100
(relative to 1980-1999)
O 2007
The area (orange/red) where there is seasonal melting at the
surface of the ice sheet in 1992 and 2002 on the Greenland Ice
Sheet
Loss of the Greenland ice mass 2003-2006 (from the GRACE experiment, Velicogna
and Wahr, September 2006, in Nature)
Alpine glaciers are important water reservoirs
during dry seasons and droughts
Hundreds of millions of people are critically
dependent on water from melting snow and ice
• Agriculture
• Hydroelectric power
• Domestic/household
• Industry
Flash floods (GLOF – Glacial Lake Outburst Floods)
Glacier retreat
•
Nearly 15000 glaciers and 9000 glacial
lakes are found in the Himalayan
mountain chain across Bhutan, Nepal,
Pakistan, India and China. The mountain
range feeds nine perennial river systems
in the region and constitutes a lifeline for
nearly 1.3 billion people downstream.
•
Himalayan glaciers are shrinking at an
average of 10 to 60 m annually, with some
retreating by 74 m a year. In China,
glaciers have been retreating at a rate of
5.5 per cent in the last three decades.
(In additions, and perhaps even more
important: Changes in the monsoon may
affect the fresh water situation in these
regions.)
•
Changes in alpine glaciers 1960-2005
Source: Kaser et al. 2006 in GRL
Projected precipitation changes
(2100 versus 2000)
The Atlantic heat conveyor is predicted to slow down in this
century (0 – 50% in different models).
• When the Golf stream
reaches north of the
Greenland-Scotland ridge
the water sinks (marked
with stars) due to low
temperature
and higher salinity than
melt water.
Nature, 2005, 438
Observed and expected increase in the
frequency of extreme weather events
IPCC 2007
4. Solutions?
Lag period in responses
•
Surface air temperature continues to rise slowly for a century or more after CO2
emissions are reduced and atmospheric concentrations stabilize
IPCC 2001
The Kyoto Protocol
• Emissions of greenhouse gasses (CO2, CH4, N20, HFK, PFK,
SF6) from industrial countries should in the period 2008 2012 be reduced by 5.2% compared to 1990.
– EU: 8% reduction
– USA: 7% reduction (Did not ratify)
– Norway 1% increase
• Carbon uptake in forests can,
up to a certain limit set
for each country, be included
• Flexible mechanisms:
– Quota trading
– Joint implementation
– Clean Development Mechanism
(Den grønne utviklingsmekanismen)
Ratification of revised protocol
• A sufficient number of countries (including Russia) have
ratified the protocol and it has now been in force since Feb.
2005
– With the important exception of the US and Australia
The Copehagen Accord
(of December 2009)
• The Accord, drafted by Brazil, China, India, South Africa, and USA, is not
legally binding and does not commit countries to agree to a binding
successor to the Kyoto Protocol (ends in 2012).
• Signatories to the Copenhagen Accord recognise that climate change is
“one of the greatest challenges of our time”, and stress strong political
will to fight it.
• Science is recognised as the basis for the actions needed in order to avoid
dangerous climate change and the IPCC’s Fourth Assessment Report is
cited as providing such information. The Accord recognises the need to
reduce global emissions enough to prevent global temperatures from
rising beyond 2 degrees Celsius.
• Emission reduction pledges under the Copenhagen Accord will likely lead
to global warming of more than 3 degrees Celsius.
Cancun 2010
• Governments agreed to limit increases in global temperature
to below 2 degrees, but
• No agreement on country measurable obligations was reached
• Measures in developing countries shall be measured,
reported, and verified in line with international guidelines
• Compensation mechanism for tropical forests protection
• Support to climate change adaptation in poorest countries
(Cancun Adaptation Framework established)
• Mechanisms for REDD (Reduced emission from Deforestation
and forest Degradation) and technology transfer
• Green Climate Fund established (shall manage the promised
fund of $ 100bn per year from 2020- to GHG reductions in dev
countries)
Per capita CO2 emissions (in tonnes) at the regional level in 2002.
The width of each bar reflects regional population, and thus the area of each bar
represents the total regional CO2 emissions
Norway’s Kyoto commitment: +1% increase; real growth 3%
Annual emissions of GHG Norway (historical and ‘Referansebanen’ and
‘Lavutslippsbanen’ 1990-2050
Cost of reducing emission of greenhouse
gasses
• Costs for industrial countries
to meet the obligations in the Kyoto Protocol (2010):
– Without international quota trading: 0.2 – 2 % of GNP
– With international quota trading: 0.05 – 1.1 % of GNP
• These estimates are very uncertain
• New technology may reduce the costs much more than
anticipated.
– Both in the US and the UK the reduction of SO2 emissions
turned out to be much cheaper the anyone had estimated
Stern Review on the economics of climate
change (2006)
• Cost of inaction: Using the results from formal economic
models, the Review estimates that if we don’t act, the
overall costs and risks of climate change will be
equivalent to losing at least 5% of global GDP each year,
now and forever. If a wider range of risks and impacts is
taken into account, the estimates of damage could rise to
20% of GDP or more.
• Cost of action: Reducing greenhouse gas emissions to
avoid the worst impacts of climate change can be limited
to a cost around 1% of global GDP each year.
Intergovernmental Panel on Climate Change (IPCC)
• Recognizing the problem of potential global climate change,
the World Meteorological Organization (WMO) and the
United Nations Environment Programme (UNEP) established
the Intergovernmental Panel on Climate Change (IPCC) in
1988.
• IPCC publishes Assessment Reports (from WG1, WG2 and
WG3) and other reports. The 4th assessment report from
WG1 was published in 2007.
• From the 4th report:
– Most of the observed increase in globally averaged temperatures since
the mid-20th century is very likely 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 to have been due to
the increase in greenhouse gas concentrations”.
5. Summary
• The CO2 (and CH4) in the atmosphere have played an
important role in determining climate over millions of years
• Present CO2 concentration in the atmosphere is the highest
for at least 650 000 years
• There are large annual variations in the net fluxes between
the atmosphere and the ocean and in particular between the
atmosphere and land areas
• There are still large uncertainties in the fluxes particularly
between atmosphere and land
• Prediction of how the these fluxes will change in the future is
highly uncertain. However, the fraction of the human-made
emissions taken up by land and ocean is likely to decrease.
Temperatures are increasing
• Surface temperature measurements show an increase in
global temperature of 0.74 (0.56 to 0.92) °C from 1906 to
2005. Global mean surface temperature for 2007 is currently
estimated at 0.41°C above the 1961-1990 annual average
– Eleven of the last 13 years rank among the warmest years
since 1850 (2007).
• Other observations support the increase in global
temperature
– Measurements in deep boreholes
– There has been an increase in the length of
growing season in Europe since the early 1960s
• Earlier inconsistencies between ground observations and
satellite measurements have largely been solved.
• Model studies show that it is very unlikely that the global
warming in recent decades is due to natural variations,
volcanic activity or changes in solar activity.
– Changes in solar activity has probably contributed to the
global warming early in the 20th century.
– There is no other reasonable explanation for the recent
increase in global temperature.
• Model calculations give fairly good agreement with observed
temperature trends.
• Observations of radiation from the Earth show changes in
agreement with enhanced greenhouse effect