climate change CO 2 (ppm) 2007 Joachim Curtius Institut für Physik der Atmosphäre Universität Mainz Contents 1. Summary 2. Background 3. Climate change: observations 4. CO 2 : ocean acidification 5. OtherGreenhouse Gases (GHGs): CH 4, N 2 O, CFCs, HFCs, O 3 6. Aerosols and Clouds 7. Solar variability 8. Future climate change 9. Paleo-climate 10. Climate protection
CO 2 -uptake by the oceans, [Orr et al., Nature, 2005]: CO 2 is dissolved in the ocean water (1.7 Pg C/yr), ~91% are present as bicarbonate ions HCO 3 ~1% as CO 2 and ~8% as carbonate ions CO 32. "Dissolved inorganic carbon" (DIC); formation of carbonic acid: CO 2 + H 2 O +CO 32 2 HCO 3 Additional CO 2 -uptake from the atmosphere leads to a decrease of the CO 32 concentration: decrease of the ph value by up to 0.3-0.4 by year 2100 expected meaning an increase in [H + ] - concentration by 100-150% [IS92a, "buisiness as usual"]. dissolution of the calcium carbonate shells (CaCO 3 ) of mussels, plankton und corals because CO 32 is sub-saturated. Southern Ocean and the subarctic Pacific are potentially sub-saturated with respect to aragonite from 2050 on. Dissolution of pteropod-plankton and corals. Orr et al., Nature, 2005: Model predictions for aragonite saturation Dissolution of pteropod shells after 48 hrs in aragonite subsaturated conditions.
Contents 1. Summary 2. Background 3. Climate change: observations 4. CO 2 : ocean acidification 5. OtherGreenhouse Gases (GHGs): CH 4, N 2 O, CFCs, HFCs, O 3 6. Aerosols and Clouds 7. Solar variability 8. Future climate change 9. Paleo-climate 10. Climate protection
non-co 2 greenhouse gases Spectral distribution of radiation from Sun and Earth in comparison to a Planck-radiator Sun: surface ~5776 C radiation maximum in the visible (0.4 0.8 µm) atmospheric radiation window, 8-12 µm
GWP "Greenhouse Warming Potential": calculates for a gas (x) on the basis of its molecular IR absorption and atmospheric life time the greenhouse warming efficiancy per molecule: referenz gas (r) is CO 2. (τ 120 years...). a time horizon(th) has always to be defined. Usually GWPs are givenfor TH of 20, 100 and 500 years. a x is the "radiationefficiency", [x(t)] gives the temporal development of the gas concentration. GWP "Greenhouse Warming Potential": 100-year and 20-year lifetime horizon [IPCC 2007]
Methane: changes and trend 1983-2006 [IPCC 2007] Sources and sinks of methane (Tg CH 4 /yr) incl. ~80-100 Tg/yr from rice paddies natural gas, oil and coal production and transport "Wiederkäuer" total: ~70% anthropogenic sources
methane sources: Keppler et al., Nature, 2006 plants emit methane! Not only microbes in the soils by anaerobic processes (e.g. methane emissions by swamps and rice paddies), contrary to previous knowledge! Unexpected, mechanism unclear! rough estimate: 10-30% (~62-236 Mt/yr) of the global sources! methane emission by plants is temperature dependent: CH 4 emissions double per 10 C increase. process could explain several observations: a) methane above tropical rain forest b) methane variations ice age - interglacial c) methane increases in the 90ies relevant for future climate prediction: forests for CO 2 -sequestration... still large surprises ahead... plants as sources of methane, Keppler et al., Nature, 2006: Methane production of dried ash und beech leaves
title of German yellow press "BILD", 1 day after Nature publication: After this, the authors published a counterstatement:...no, the trees are not to blame... Methane: long-lived, well-mixed trace gas, concentration ~1750 ppbv life-time: 8.9 (and 12 years perturbation time) largest sink (>85%): OH reaction CH 4 + OH CH 3 + H 2 O feedback: CH 4 consumes OH, therefore: the higher CH 4 concentration, the less OH (+1% CH 4 corresponds to 0.32% OH): This prolongates the CH 4 degradation bya factor of 1.4. (perturbation time) estimated direct radiative forcing by anthropogenic CH4: 0.48 W m-2 (IPCC 2001,2007)
Methane: not only direct effect as a GHG, but altogether 4 indirect effects: * longer lifetime from OH consumption * productionof tropospheric ozone * CO 2 is degradationproduct of methane * stratospheric water vapour increases due to CH 4 Methane: 4 indirect effects [IPCC 2007]
Methan: zeitliche Entwicklung der letzten 1000 Jahre Methane: development over the last 650 000 years [Spahni et al., Science, 2005] similar to CO 2, concentrations of CH 4 and N 2 O in the last 650 000 years have always been well below todays values.
Methane: future development depends strongly on assumed scenario Expected change in methane lifetimes due to OH feedback:
Methane releases from russianoil and gas pipelines? Lelieveld et al., Nature, 2005: CH 4 flux measurements by helicopter... release is small:~1.4% therefore, substitution of coal and oil by gas is beneficial because not only less CO 2 per kwh is produced but also the total RF is reduced (despite the lareger GWP of CH 4. Non-CO 2 greenhouse gases
N 2 O: sources and sinks (Tg N/yr) total: ~ 60% anthropogenic sources, mainly from manure production and manure soil processing N 2 O: Change in N 2 O 1978-2006 (pre-industrial: ~270 ppb). [IPCC 2007]
N 2 O: future development also strongly scenario dependant non-co 2 greenhouse gases: halogen-containing GHGs very large Greenhouse Warming Potentials: e.g. SF 6...
halogencontaining LLGHGs: development since 1978 After Montreal Protocol, no further increase, or even decrease of CFCs but strong increase of substitutes. [IPCC 2007] Halogen compounds: future development
Tropospheric ozone: very variable, averages and trends difficult to assess Chemistry strongly influenced by NO x, CO, CH 4 and VOCs, UV light, etc. therefore these gases are considered "indirect" greenhouse gases. "precursor substances" have strong anthropogenic sources ("Smog"), e.g.: NO x -katalyzed CO oxidation. ground-level ozone decreasing in Europe and North America, increasing in Southeast Asia and in the Near East. not only a greenhouse gas but also important due to ist impacts on human health and agricultural production Ozone trends at mid latitudes of the Northern Hemisphere
future trends of tropospheric ozone radiative forcing 1750-2000 in W/m 2 a) by long-lived greenhouse gases CO 2, CH 4, N 2 O, CFCs c) byozone
Methan decomposition in the atmosphere [Lelieveld et al., Tellus B, 1998]