Climate Change Information Seminar Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) – the relevance to FAO’s activities Claudia Hiepe Hideki Kanamaru NRCB Nov 27th Tuesday 14:00-15:30 German Room Dec 3rd Monday 10:00-11:30 Iran Room

Three Volumes of IPCC Fourth Assessment Report (AR4) WG1 152 authors, 600 reviewers, 996pp., technical summary 74pp. WG2 173 lead authors, 183 contributing authors, 910 reviewers, 976pp., technical summary 56pp. WG3 168 lead authors + 85 contributing authors, 485 reviewers, 896pp., technical summary 70 pp.

IPCC 2007 WG 1 – The Physical Science Basis Observed Changes in Climate Attribution of Change Projected Change

Observed changes since 1850

Precipitation trend

Detection of Climate Change Observed change is significantly different (statistically) than natural internal variability of climate. Virtually certain > 99% probability Extremely likely > 95% probability Very likely > 90% probability Likely > 66% probability Very high confidence : at least 9 out of 10 chance of being correct High confidence : about 8 out of 10 Medium confidence : about 5 out of 10

Observed trends in climate with respect to natural internal climate variability Drought affected area increased since 1970s. (likely) Cold days and nights have become less frequent, hot days and hot nights have become more frequent over the past 50 years. (very likely) Heat waves have become more frequent. (likely) Heavy precipitation events have become more frequent. (likely) Average NH temperatures during 2 nd half of the 20 th century were higher than during any other 50-year period in the last 500 years (very likely) and the highest in at least the past 1300 years (likely).

Observed Changes in Natural and Human Environments due to recent warming Earlier timing of spring events. (very high confidence) Poleward and upward shifts in plant and animal ranges. (very high confidence) Shifts in ranges and changes in algal, plankton and fish abundance in some marine and freshwater systems. (high confidence) Agricultural and forestry management at NH higher latitudes – earlier spring planting of crops and alterations in disturbance regimes of forests due to fires and pests. (medium confidence)

Attribution of Change Demonstrate that observed changes are –Unlikely to be entirely within internal climate variability. –Consistent with estimated responses to external anthropogenic forcings, i.e., most importantly GHG emissions. –Not consistent with other explanations. Most of the observed increase in globally-averaged temperatures since the mid-20 th century is due to the observed increase in anthropogenic GHG concentrations. (very likely); on continental scale (likely); regional and smaller scales (attribution is difficult)

Changes in surface temperature since 1900 – obs vs model

GHG concentrations variations over the last 10,000 years CO2 CH4 N2O Global GHG emissions have grown since pre- industrial times, with an increase of 70% between 1970 and (high agreement, much evidence)

Human Activities and GHGs Global increases in CO2 concentrations are due primarily to fossil fuel use, with land-use change providing another significant but smaller contribution. CH4 concentration increase is predominantly due to agriculture and fossil fuel use. The increase in N2O concentration is primarily due to agriculture (fertilizers).

Global average radiative forcing warmingcooling The net effect of human activities since 1750 is warming. (very high confidence)

Projected Changes Global GHG emission will continue to grow over the next few decades with current policies and practices. (high agreement and much evidence) Further warming during the 21 st century would be larger than those observed during the 20 th century. (very likely) For the next two decades: 0.2 °C per decade for a range of emissions scenarios. 0.1 °C per decade even if GHG concentrations had been kept constant at year 2000 levels projection relative to °C increase

Surface warming projections

Projected surface temperature changes Warming greatest over land and high latitudes NH. Warming least over Southern Ocean and parts of the North Atlantic Ocean.

Precipitation changes for the period , relative to Precipitation increases in high latitudes. (very likely) Precipitation decreases in most subtropical land regions. (likely)

Projections of extreme events Warmer and fewer cold days and nights, warmer and more frequent hot days and nights (Virtually certain) Increase in frequency of hot extremes, heat waves, and heavy precipitation. (very likely) Increase in tropical cyclone intensity, drought affected area. (likely)