climatic stressors major recent changes and projections in the central and south

Climate Change 2014:

Jose A. Marengo

CCST INPE

Sao Paulo, Brazil

jose.marengo@inpe.br

CLIMATIC STRESSORS: MAJOR RECENT CHANGES AND PROJECTIONS IN THE CENTRAL AND SOUTH AMERICA: MAIN RESULTS OF CHAPTER 27 CENTRAL AND SOUTH AMERICA OF THE IPCC AR5 WG2

IPCC SPM WG1 (2013)

Executive Summary: Observed trends

Significant trends in precipitation and temperature have been observed in CA and SESA (high confidence ). Besides, changes in climate variability and in extreme events have severely affected the region (medium confidence ).

Increasing trends in annual rainfall in Southeastern South America (SESA; 0.6 mm/day/50years during 1950-2008) contrast with decreasing trends in CA and Central-Southern Chile (-1mm/day /50 years during 1950-2008). Warming has been detected throughout CA and SA (near to 0.7-1°C/40 years since the mid-1970’s), except for a cooling off the Chilean coast of about -1 °/40 years. Increases in temperature extremes have been identified in CA and most of tropical and subtropical SA (medium confidence), while more frequent extreme rainfall in SESA has favoured the occurrence of landslides and flash floods (medium confidence).

IPCC WG2, Chapter 21 (2014)

Risk of climate-related impacts results from the interaction of climate-related hazards (including hazardous events and trends) with the vulnerability and exposure of human and natural systems. Changes in both the climate system (left) and socioeconomic processes including adaptation and mitigation (right) are drivers of hazards, exposure, and vulnerability.

Projected changes in annual average temperature and precipitation. CMIP5 multi-model mean projections of annual average temperature changes (left panel ) and average percent change in annual mean precipitation (right panel) for 2046-2065 and 2081-2100 under RCP2.6 and 8.5. Solid colors indicate areas with very strong agreement, where the multi-model mean change is greater than twice the baseline variability, and>90% of models agree on sign of change.

Warm nights 1951-2010Consecutive dry days 1951-2010 Heavy precip days 1951-2010

Consecutive dry days 1951-2003 Warm nights 1951-2003Heavy precip days 1951-2003

Alexander et al (2006)

Donat et al (2013)

Stations coverage

Decay

Improve

Executive Summary: Projeted trends

Climate projections suggest increases in temperature, and increases or decreases in precipitation for CA and SA by 2100 (medium confidence ).

Post-AR4 climate projections, derived from dynamic downscaling forced by CMIP3 models for various SRES scenarios, and to different global climate models from the CMIP5 for various RCPs (4.5 and 8.5), warming varies from +1.6°C to +4.0°C in CA, and +1.7°C to +6.7°C in SA (medium confidence). Rainfall changes for CA range between -22% to +7% by 2100, while in SA rainfall varies geographically, most notably showing a reduction of -22% in Northeast Brazil, and an increase of +25% in SESA (low confidence). By 2100 projections show an increase in dry spells in tropical SA east of the Andes, and in warm days and nights in most of SA (medium confidence)

Key messages

• Observation systems are improving and hence our assessment is better than AR4

• There are very major gaps (Africa, S. America..)

• Linking climatic, biophysical and human data is a promising way to improve impacts assessment

• This allows us to distinguish climate change impacts from consequences of other aspects of policy and development

• Many impacts may not have been observed, but that does not mean that no impacts have occurred.