Cambiamento attuale: Biogeochimica CLIMATOLOGIA Prof. Carlo Bisci

Rainfall, runoff and evapotranspiration derived from climate simulation results of Hahmann (Amazon) and Wang and Eltahir (Africa) at the equator. Both studies examined the differences between ‘ uniform ’ precipitation over a model grid square and ‘ variable ’ precipitation (added to about 10% of the grid square). Large differences are seen between the two cases in the two studies: a large reduction in precipitation is seen in the Hahmann variable case relative to the uniform case, whereas an increase is seen for the Wang and Eltahir variable case. The differences are even greater for runoff: Hahmann ’ s uniform case runoff is three times as large as the variable case, whereas Wang and Eltahir have almost no runoff for their uniform case.

Coupling strength between summer rainfall and soil water in models, divided into how strongly soil water causes evaporation (including from plants) and how strongly this evaporation causes rainfall. The soil water-precipitation coupling is scaled up by a factor of 10, and the two indices for evaporation to precipitation coupling given in the study are averaged.

The global carbon cycle: pre-industrial ‘ natural ’ annual fluxes are in black and ‘ anthropogenic ’ fluxes in red.

The global carbon budget (GtC yr – 1 ); errors represent ±1 standard deviation uncertainty estimates and not interannual variability, which is larger. The atmospheric increase (first line) results from fluxes to and from the atmosphere: positive fluxes are inputs to the atmosphere (emissions); negative fluxes are losses from the atmosphere (sinks); and numbers in parentheses are ranges. Note that the total sink of anthropogenic CO 2 is well constrained. Thus, the ocean-to-atmosphere and land-to-atmosphere fluxes are negatively correlated: if one is larger, the other must be smaller to match the total sink, and vice versa.

Changes in global atmospheric CO 2 concentrations. (a) Annual (bars) and five-year mean (lower black line) changes in global CO 2 concentrations. The upper stepped line shows annual increases that would occur if 100% of fossil fuel emissions remained in the atmosphere, and the red line shows five-year mean annual increases. (b) Fraction of fossil fuel emissions remaining in the atmosphere ( ‘ airborne fraction ’ ) each year (bars), and five-year means (solid black line; mean since 1958 is 0.55). Note the anomalously low airborne fraction in the early 1990s.

Individual estimates of the ocean- atmosphere flux and of the related land- atmosphere flux required to close the global carbon budget. The dark thick lines are the revised budget estimates for the 1980s, the 1990s and the early 2000s, respectively.

The geographical distribution of the buffer factor in ocean surface waters in High values indicate a low buffer capacity of the surface waters. The Revelle factor (or buffer factor) as a function of CO 2 partial pressure (for temperature 25°C, salinity 35 psu, and total alkalinity 2,300 µ mol kg – 1.

Model projections of the neutralization of anthropogenic CO 2 for an ocean-only model, a model including dissolution of CaCO 3 sediment and a model including weathering of silicate rocks, (top) for a total of 1,000 GtC of anthropogenic CO 2 emissions and (bottom) for a total of 5,000 GtC of anthropogenic CO 2. Without CaCO 3 dissolution from the seafloor, the buffering of anthropogenic CO 2 is limited. Even after 100 kyr, the remaining pCO 2 is substantially higher than the pre-industrial value.

Uncertainties in carbon cycle feedbacks; each effect is given in terms of its impact on the mean airborne fraction over the simulation period (1860 to 2100), with bars showing the uncertainty range. The lower three bars are the direct response to increasing atmospheric CO 2, the middle four bars show the impacts of climate change on the carbon cycle, and the top black bar shows the range of climate-carbon cycle feedbacks given by the C 4 MIP models.

Schematic representation of the multiple interactions between tropospheric chemical processes, biogeochemical cycles and the climate system. RF represents radiative forcing, UV ultraviolet radiation, T temperature and HNO 3 nitric acid.

Probability that the daily maximum eight-hour average ozone concentration will exceed the US National Ambient Air Quality Standard of 0.08 ppm for a given daily maximum temperature based on 1980 to 1998 data. Values are shown for New England, the Los Angeles Basin and 122.5°W) and the southeastern USA

Sources, sinks and atmospheric budgets of CH 4

(Changes in the emissions of fuel combustion NO x and atmospheric N 2 O mixing ratios since Mixing ratios of N 2 O provide the atmospheric measurement constraint on global changes in the N cycle. Changes in the indices of the global agricultural N cycle since 1850: the production of manure, fertilizer and estimates of crop N fixation.

SatelliteModelli

Global sources (TgN yr – 1 ) of NO x, NH 3 and N 2 O for the 1990s

Summary of global budget studies of atmospheric H 2 (Tg(H 2 ) yr – 1 ).

(a) Chinese desert distributions from 1960 to 1979 and desert plus desertification areas from 1980 to (b) Sources (S1 to S10) and typical depositional areas (D1 and D2) for Asian dust