Is our global warming anthropogenic?

Georgy Golitsyn, A. M. Obukhov Institute for Atmospheric Physics
February 27th, 2009 at 11AM–12PM in 939 Evans Hall [Map]

The talk will follow several US NRC reports starting with 1979 and IPCC FAR (Fourth Assesment Report, 2007) added by personal and Russian experience with minimum slides. In 1906–2005 the annual mean global temperature has increased by 0.74 °C = 1.33 °F, with more than half increase during last third of the century. Such rapid changes are unknown in the Earth's history Examples. Cooling of the winter stratosphere and mesosphere by 10 °C – 30 °C is another example of the global change since IGY, 1957. The 1990s were the decade of mitigation and prevention of natural catastrophes. During this period losses from catastrophes of geophysical origin: earthquakes, volcanoes, etc. were more or less level while the losses from the ones of meteorological origin nearly doubled.

The main greenhouse gas, GHG, in our climate system is water vapour, then rated by their effects are CO2, methane, CFCs, O3, N2O, etc. The GHG-effect is that the atmosphere is more transparent to the incoming solar radiation than to outgoing thermal IR. When IR opacity increases then part of the additionally absorbed IR is radiated back warming up the surface. There is the antiGHG-effect, dust storms on Mars and here, “nuclear winter” (solar radiation is absorbed more by the atmosphere than surface IR).

Thermodynamics: Clapeyron–Clausius equation, es(τ) - exponential, the warming of the water surface increases atmospheric water vapour: chief positive feedback, clouds are mostly negative feedback: US DOE ARM Program. Aerosol: dust volcanic, organic, human made.

Residence times. Models: solar, IR, aerosol, etc. Climate – statistics of weathers. ECMRWF: 512 harmonics, ∼50 levels in the vertical, 10 day forecast is mean of 10 forecasts from tiny different initial conditions, a hundred teraflop computers. Climate change models ∼42,84 harmonics, ∼20 levels in the vertical, ocean-better resolution. Parameterizations: expression of subgrid processes through variables computed at the grid, e.g. air–sea interaction.

Model sensitivities. Test of the model performance: XX century, 1950 – u/p: reanalysis of global weather maps, every 6 hours, several levels. PDF for vortices on (δp)², geostrophy, exponential, but different for cyclones and anticyclones at high tails, hurricanes PDF also exponential, as well as tornadoes and dust devils.

Model prediction: in warmer climate more intense hydrological cycle, but less rain days more days with intense rains, i.e. more probability for both droughts and floods (Vladimir Semenov, IAP and Kiel). Found for US by Pavel Groisman (NCC Ashville, N.C.)

Solar activity: δT ≈ 0.2 °C.

Paleoevidence: 7 ice ages, holocene optimum ΔT ∼ 1 °C but for several hundred years, not in Tasmania, never high trends global or regional? Little ice age 1640–1820, more regional. 20000 y BP ΔT ∼ −5 °C, 10000 yr - 5 °C – 0.05 °C/100 yr.

Cretaceous 120–60 MyBP: ΔT ∼ +5 °C, warm Arctic + Siberia, due to CO2. 55 My ± 100 ky, ΔT = + several °C, due to CH4 sudden release.

Main aims: regional changes with better models, PDFs for anomalies as TC, PL, tornadoes, etc. Many better specialists in particular areas are in US!