Climate in Asia and the Pacific: Climate Variability and Change

Abstract

The geographic extent of Asia and the Pacific leads to great variation in the climate of the region. Major influences on global climate arise from the scale and elevation of the Himalayan Tibetan Plateau (HTP), and from the air-sea interactions in the Pacific associated with the El Niño–Southern Oscillation (ENSO). The monsoon has a profound effect on the climate of Asia, with its strong seasonal cycle. Variability is also caused by ENSO, the Indian Ocean Dipole (IOD) and Pacific Decadal Oscillation (PDO). ENSO is the principal source of inter-annual global climate variability. ENSO has significant climate and societal impacts on both regional and global scales. The climate effects of ENSO are modulated on decadal time scales by the PDO. IOD affects the climate in the Indian Ocean and Australasia. Climate observations show significant warming trends in temperature across Asia and the Pacific; not only is there an increase in mean temperature, but there is more warming in North Asia and less in the Pacific during the twentieth century. Observed trends in precipitation are more variable, with some evidence of increasing intensity of storms. Glacier mass balance studies show dramatic decline in ice mass in the Himalayas and New Zealand, with monitored ice mass losses of 0.3–0.5 km2/year, in the last three decades. Temperature extremes have changed region wide: cool nights, cold days have very significantly decreased universally, and the frequency of hot days has increased. Projections of future climate change for the region suggest longer summer heat waves in South and East Asia and Australia, and increases in precipitation in several areas. Regional downscaling techniques are used to project future climate: warming is projected to be largest in high latitude (Northern Asia, Central Asia) and high altitude (Tibetan Plateau) regions; with a suppression of the south Asian summer monsoon, along with a delay of monsoon onset and increase of monsoon break periods. Monsoon precipitation is projected to increase over South Asia.