Glossary from "Climate Change 2007: Working Group I: The Physical Basis of Climate Change" by IPCC (2007)
Glossary of Terms used in the IPCC Third Assessment Report (2001)
Climate change: a glossary by the IPCC (1995)
Glossary of Climate Change Terms from the Environmental Protection Agency (EPA) of the U.S.

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2007 Nobel Peace Prize - the HKO connection (15 October 2007)

Projected Change in Hong Kong's Rainfall in the 21st Century (26 August 2005)

Visibility in Hong Kong is Worsening, Reduced Visibility Hits Record High in 2004 (6 January 2005)

Temperature projections for Hong Kong in the 21st Century (19 August 2004)

HKO announces findings on long-term sea level change in Hong Kong (14 June 2004)

Global warming - the Hong Kong connection (1 August 2003)

This Educational Package represents an efforts by the Hong Kong Observatory to promote public awareness of climate change. It is intended to help people appreciate what climate change is and understand its serious impacts.

Hopefully people would be motivated to act as responsible individuals, helping to reduce carbon dioxide emission by all available means, so as to give the Earth a chance to recover. In this endeavour, the Observatory would be happy to work alongside the education sector and non-government organizations to defend our beautiful Earth which we call home, for the sake of the people of Hong Kong as well as all mankind.

Thermohaline circulation (also called Great Ocean Conveyor belt) is a large-scale density-driven circulation in the ocean, caused by differences in temperature and salinity. In the North Atlantic the thermohaline circulation consists of warm surface water flowing northward and cold deep water flowing southward, resulting in a net poleward transport of heat. The surface water sinks in highly restricted sinking regions located in high latitudes.

According to IPCC (Climate Change 2007: Working Group I: Physical Science basis, Summary for Policymakers), it is very likely that the thermohaline circulation of the Atlantic Ocean will slow down during the 21st century. It is very unlikely that the thermohaline circulation will undergo a large abrupt transition during the 21st century. Long-term changes in the thermohaline circulation cannot be assessed with confidence.

Detailed information about thermohaline circulation can be found at United Nations Environment Programme (UNEP)

El Nino is a local warming of surface waters which takes place in the entire equatorial zone of the central and eastern Pacific Ocean off the Peruvian coast and which affects the atmospheric circulation world-wide. El Nino usually peaks around Christmas, hence the name of the phenomenon (Spanish for "the little boy" or "the Christ Child"). It occurs on average every three to five years, lasting 12 to 18 months.

La Nina, "the little girl" in Spanish, is characterized by below-normal sea surface temperatures in the eastern equatorial Pacific. La Nina occurs less frequently compared with El Nino. La Nina conditions typically last approximately 9 to 12 months.

The Southern Oscillation is an east-west balancing movement of air masses between the Pacific and the Indo-Australian areas. It is roughly synchronized and associated with typical wind patterns and El Nino, and measured by the Southern Oscillation Index (SOI), the difference between sea level atmospheric pressures at Darwin and Tahiti.

El Nino is the oceanic component, while the Southern Oscillation is the atmospheric one. This combination gives rise to the term ENSO. In general, large negative values of the SOI are associated with warm events.

ENSO conditions are commonly defined with reference to the sea surface temperatures in the Nino regions (see figure below). Latest conditions of ENSO can be found at http://www.weather.gov.hk/wxinfo/climat/enso.htm.

The local impacts of ENSO can be found in the following references prepared by HKO staff:

Some Impacts of El Nino and La Nina Events on the Weather of Hong Kong (June 1999)
El Nino and Hong Kong Rainfall (January 1998, in Chinese only)
The effect of ENSO and East Asian Monsoon on the annual rainfall in Hong Kong, China (May 2004)
Effect of ENSO on Number of Tropical Cyclones Affecting Hong Kong (Feburary 2002)
Impacts of El Nino-Southern Oscillation Events on Tropical Cyclone Landfalling Activity in the Western North Pacific (March 2004)
El Nino and Tropical Cyclones over the western North Pacific ( January 1998)
Variations in Tropical Cyclone Activity in the South China Sea ( November 2006)
Tropical cyclone activity over the western North Pacific - From El Nino to La Nina (April 1991)

The Pacific Decadal Oscillation (PDO) is the predominant source of inter-decadal climate variability in the Pacific Northwest. Like ENSO, PDO is characterized by changes in sea surface temperature, sea level pressure, and wind patterns. The PDO is described as being in one of two phases: a warm phase and a cool phase.

The warm phase of PDO favors anomalously warm sea surface temperatures near the equator and along the coast of North America, and anomalously cool sea surface temperatures in the central North Pacific. The cool phase for PDO has the opposite pattern of SST anomalies. Each PDO phase typically lasts for 20-30 years.

Detailed information and the latest condition of the PDO can be found at http://jisao.washington.edu/pdo/.

The influence of PDO on the summer rainfall in southern China (and Hong Kong) can be found in the paper "Regime Shift in Summer Rainfall in Southern China" prepared by HKO staff. Moreover, the tropical cyclone activity in the South China Sea is likely to be modulated by PDO as shown in the HKO's paper "Variations in Tropical Cyclone Activity in the South China Sea".

The Arctic Oscillation (AO) is an important Arctic climate index with positive and negative phases, which represents the state of atmospheric circulation over the Arctic. The positive phase brings lower-than-normal pressure over the polar region, steering ocean storms northward, bringing wetter weather to Scotland and Scandinavia, and drier conditions to areas such as Spain and the Middle East. While the value of the AO index was strongly positive in the early 1990's compared to the previous forty years, the value of the AO has been low and variable for the last nine years.

Further iformation of the AO can be found at http://www.cgd.ucar.edu/cas/jhurrell/indices.html

From the paper "Relationship between Winter Temperature in Hong Kong and East Asian Winter Monsoon", the AO would be related to the strength of the East Asian winter monsoon and the winter temperature in Hong Kong.

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    Working Group III Summary "Mitigation of Climate Change"
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Global Warming pages by World Meteorological Organization (WMO)
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Chinese Climate Change Network by China Meteorological Adminstration (CMA)
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