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HONG KONG IN A WARMING WORLD SECOND EDITION THE WORLD Contents THE WORLD 1 Unprecedented carbon dioxide concentration........................ 2 2 Abrupt temperature rise...................................................... 3 THE WORLD 3 Melting of ice and snow...................................................... 4 4 Mean sea level rise............................................................ 5 5 More extreme heat............................................................. 6 6 Enhanced water cycle......................................................... 6 7 Projection of global climate for the 21st century..................... 7 HONG KONG 8 Climate change in Hong Kong........................................... 12 9 Projection of Hong Kong climate for the 21st century............15 Mitigating climate change – our role and responsibilities.......21 10 Adapting to climate change – be prepared.......................... 23 11 Collaborative effort in combating climate change................. 25 12 Useful links.......................................................................... 27 Appendix............................................................................. 28 Source of figures and data..................................................... 29 Photo credits........................................................................ 29 Warming of the climate system is unequivocal, and since the 1950s, many of the observed changes are unprecedented over decades to millennia. It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century. The Fifth Assessment Report (AR5) of Working Group I of the Intergovernmental Panel on Climate Change (IPCC) 1 THE WORLD 1 THE WORLD Unprecedented carbon dioxide concentration 2 The atmospheric concentration of carbon dioxide (CO2), the most important greenhouse gas as well as the main driver of global climate change in the last century, has increased by over 40 per cent since pre-industrial times. The increase is primarily due to burning of fossil fuels and secondarily due to deforestation. Present-day concentration of CO2 is the highest in the last 800,000 years. FIGURE 1 Highest in the last 8OO,OOO years 350 FIGURE 2 Warming trend during 1901-2012 the warmest since 185O. 4O%+ 400 With heat trapped by the increasing presence of greenhouse gases, almost every corner of the globe has experienced a warming trend throughout the 20th century. The first decade of the 21st century has been Atmospheric carbon dioxide concentration in the last 800,000 years ppm Abrupt temperature rise (OC) The recent warming is so abrupt that it has totally reversed the long-term cooling trend in the last 5,000 years. FIGURE 3 Global temperature anomalies with respect to 1961-1990 300 O C 0.8 250 0.4 200 0 150 800,000 700,000 600,000 500,000 400,000 300,000 200,000 100,000 0 -0.4 uncertainty average -0.8 -1.2 10,000 Check the latest atmospheric CO2 levels here: 2 8,000 6,000 4,000 2,000 0 number of years before 1950 Latest global average surface temperature anomaly relative to 1951-1980: 3 THE WORLD THE WORLD 3 Melting of ice and snow The warming climate has contributed to widespread melting of snow cover, ice caps, mountain glaciers and ice sheets over Greenland and West Antarctica. Reduction of reflective surfaces of ice and snow will in turn mean more heat absorbed as the Earth’s ability to disperse sunlight back to space is compromised. This is expected to accelerate the melting of ice and snow – a vicious cycle. 4 FIGURE 4 Arctic sea ice decrease from 1980 (upper) to 2012 (lower) Mean sea level rise Thermal expansion of sea water and melting of land-based ice and snow will lead to a global sea level rise. The rate of sea level rise since the mid-19th century has apparently accelerated when compared to the mean rate in the previous two millennia. FIGURE 5 198O Global average sea level change relative to 1900-1905 mm 200 2O12 150 100 50 MUIR GLACIER , ALASKA Different coloured lines represent different independent data sets 0 -50 1900 1941 1920 1940 2OO4 4 Latest Arctic sea ice extent: Latest glacier mass balance: Mass variation of Antarctic and Greenland Ice Sheets: 1980 2000 year Rising sea level will cause coastal flooding and accentuate the threat of storm surges brought by cyclones. Melting of Muir Glacier, Alaska’s Glacier Bay from 1941 (left) to 2004 (right) Short video on the largest Greenland glacier calving ever filmed: 1960 Storm surge caused by Hurricane Sandy along the east coast of the United States in 2012 Latest sea level change: 5 THE WORLD 5 THE WORLD 7 More extreme heat A warming climate increases the chance of extreme heat. The number of cold days and nights has decreased and the number of warm days and nights has increased on the global scale. 27 December 2013 - 3 January 2014 The frequency of heat waves has increased in many parts of Europe, Asia and Australia. 6 0 TEMPERATURE The world moved along the trajectory of a high greenhouse gas concentration pathway in the past decade. Although implementation of the pledges of targets for emission reduction by 2030 made by countries attending the Paris climate summit (COP21) in 2015 could steer the world away from the worst scenario, it is evident that based on the climate projections by IPCC AR5, much more effort will be required from now on if we aim to reach the COP21 target of keeping global temperature rise below 2ºC (relative to pre-industrial levels) by the end of this century. FIGURE 6 Land surface temperature anomaly over Australia ≤-15 Projection of global climate for the 21st century Much more effort required to keep global temperature rise below 2ºC ≥15 (oC) Enhanced water cycle Ocean warming leads to more evaporation of sea water. A warmer atmosphere has the capacity to hold more water vapour, thereby increasing the chance of heavy rain. More land areas have experienced an increase in heavy precipitation since the mid20th century. COP 21, Paris Based on the pledges made at COP21, the world could still be heading towards a temperature rise of around 3°C (relative to pre-industrial levels) by the end of this century. It is virtually certain that there will be more hot temperature extremes and fewer cold temperature extremes over most land areas as global mean temperature increases. Heat waves will occur with a higher frequency and duration despite the occasional episodes of cold winter extremes. Heavy rain in Shenzhen on 11 May 2014 6 7 THE WORLD THE WORLD PRECIPITATION FIGURE 7 Carbon dioxide emissions associated with different greenhouse gas concentration scenarios billion tonne/year High 100 80 Worst scenario Country pledges for 2030 60 FIGURE 9 Medium-high 2015 40 20 0 In a warmer world, extreme precipitation events will very likely become more intense and more frequent over most of the mid-latitude land masses and over wet tropical regions by the end of this century. Projected percentage change in 20-year return values of annual maximum daily precipitation for 2081-2100 per unit local temperature increase (°C) relative to 1986-2005 Medium-low Historical observations 2ºC target scenario Extreme precipitation events will very likely become more intense and more frequent. Low -20 1980 2000 2020 2040 2060 2080 2100 year FIGURE 8 Projected regional temperature change (°C) for 2081-2100 per unit global average temperature increase (°C) relative to 1986-2005 FIGURE 1O Projected percentage change in global average annual maximum 5-day precipitation over land regions for different greenhouse gas concentration scenarios relative to 1981-2000 % relative change Historical simulation (up to 2005) Low Medium-low High 20 15 10 5 ºC per ºC increase in global mean 0 -5 8 1960 1980 2000 2020 2040 2060 2080 2100 year 9 THE WORLD THE WORLD DROUGHT The risk of drought remains in many parts of the world with substantial increases in soil dryness projected in the Mediterranean, Europe, North and South Americas, southern Africa and China. FIGURE 11 Projected changes in annual mean surface soil moisture in 2081-2100 relative to 1986-2005 Low concentration scenario HONG KONG High concentration scenario (mm) SEA LEVEL In a warmer world, most of the coastline will be affected by sea level rise. Even for the medium-low and medium-high greenhouse gas concentration scenarios, which are the more likely scenarios after COP21, the impact of sea level rise on coastal communities will still be significant. Hong Kong is not immune to climate change. FIGURE 12 Projected global mean sea level rise relative to 1986-2005 m 1.0 0.8 0.6 High concentration scenario Median Likely range Low concentration scenario Median Likely range 0.4 0.2 0 2000 10 2020 2040 2060 2080 2100 year Projected regional mean sea level rise for 2081-2100: 11 HONG KONG HONG KONG 8 Climate change in Hong Kong FIGURE 14 Changes in the annual number of hot nights, very hot days and cold days TEMPERATURE 40 th Since the late 19 century, Hong Kong has experienced a significant warming trend. Both global warming and effects of local urbanization contribute to the warming, with the latter estimated to contribute up to 50% of the warming. 30 More frequent Annual number of hot nights Annual number of very hot days Annual number of cold days 10 0 FIGURE 13 Rarer 20 1885-1914 1986-2015 Annual mean temperature recorded at the Hong Kong Observatory headquarters (1885-2015) Data are not available from 1940 to 1946 ºC 24.5 24.0 PRECIPITATION A significant warming trend Extreme precipitation events have become more frequent. The hourly rainfall record at the Hong Kong Observatory headquarters was broken several times in the last few decades, whereas it used to take several decades to break the record in the past. 23.5 23.0 More frequent extreme precipitation FIGURE 15 22.5 Hourly rainfall records (1885-2015) 22.0 mm 160 21.5 2008: 145.5mm 140 21.0 1885 1895 1905 1915 1925 1935 1945 1955 1965 1975 1985 1995 2005 2015 1885-2015 +0.12 °C/decade 1986-2015 +0.17 °C/decade year 2006: 115.1mm 120 1966: 108.2mm 1992: 109.9mm 1926: 100.7mm 100 1886: 88.4mm 80 Over the last century, the number of hot nights (daily minimum temperature ≥ 28ºC) and very hot days (daily maximum temperature ≥ 33ºC) in Hong Kong has increased by manifold while the number of cold days (daily minimum temperature ≤ 12ºC) has decreased significantly. 12 60 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 year Latest temperature trend in Hong Kong: Trends in extreme weather events in Hong Kong: 13 HONG KONG HONG KONG of Hong Kong climate for 9 Projection st the 21 century SEA LEVEL Tide gauge records in Victoria Harbour since 1954 show an unambiguous rise of mean sea level. TEMPERATURE If the emission reductions agreed at COP21 materialize, the mediumlow to medium-high greenhouse gas concentration scenarios would be more likely than the other two scenarios. In such cases, a rise of 1.5 to 3.5°C (relative to 1986-2005) in the decade of 2091-2100 is expected. FIGURE 16 Annual mean sea level at Victoria Harbour Sea level above Chart Datum (m) 1.6 1.5 1954-2015 +30 mm/decade FIGURE 17 1.4 Projected changes in the annual temperature of Hong Kong under different greenhouse gas concentration scenarios 1.3 relative to 1986-2005 1.2 ºC Annual mean temperature 6 5 1.0 1950 1960 1970 1980 1990 2000 2010 year in 2091-2100 4 Medium-high Medium-low 3 Latest trend in mean sea level in Hong Kong: High 1.5-3.5ºC 1.1 10-year average temperature anomaly 2 Low 1 likely range for 2091-2100 0 -1 2000 2010 2020 Observed High Medium-high 14 2030 2040 2050 2060 2070 2080 2090 2100 year Medium-low Low 15 HONG KONG HONG KONG Even under the medium-low and medium-high greenhouse gas concentration scenarios, the annual numbers of hot nights and very hot days are expected to continue rising significantly in the 21st century, while the annual number of cold days is expected to drop. 12 FIGURE 18 Projected annual number of hot nights, very hot days and cold days in Hong Kong under the medium-low and high greenhouse gas concentration scenarios 160 FIGURE 19 Future changes in extremely wet and extremely dry years under the medium-low and high greenhouse gas concentration scenarios 160 Observed 160 Mediumlow 120 120 120 80 80 80 40 40 40 0 0 1986-2005 High 2091-2100 Mediumlow 12 12 8 8 8 4 4 4 0 1885-2005 0 2006-2100 2051-2060 Annual number of hot nights Annual number of very hot days Annual number of cold days 2091-2100 year Projection of hot nights, very hot days and cold days for all scenarios: 0 2006-2100 year The year-to-year and decade-to-decade variations of rainfall will remain large. However, as temperature continues to increase in the 21st century, extreme rainfall is also expected to increase. FIGURE 2O Projected annual maximum daily rainfall and annual Extreme rainfall maximum 3-day rainfall in Hong Kong under the medium- expected to increase low and high greenhouse gas concentration scenarios mm mm 600 PRECIPITATION Except for the low greenhouse gas concentration scenario, the annual rainfall is expected to generally increase towards the end of this century. Of even more interest is the remarkable increase in extremely wet years (annual rainfall > 3168 mm) in 2006-2100 for all the scenarios while the number of extremely dry years (annual rainfall < 1289 mm) is expected to remain about the same. Observed 600 mm Mediumlow 600 400 400 400 200 200 200 0 1986-2005 0 2051-2060 2091-2100 0 High 2051-2060 Annual maximum daily rainfall Annual maximum 3-day rainfall Projection of extremely wet and extremely dry years for all scenarios: 16 High Extremely wet years Extremely dry years 0 2051-2060 Observed Remarkable increase in extremely wet years 2091-2100 year Extreme rainfall projection for all scenarios: 17 HONG KONG HONG KONG SEA LEVEL STORM SURGE Regardless of the greenhouse gas concentration scenario, the mean sea level in Hong Kong and its adjacent waters is expected to rise further in the 21st century. Apart from high winds and heavy rain, storm surge is also a threat posed by approaching tropical cyclones. Over the last hundred years or so, several typhoons (e.g. in 1874, 1906, 1937 and 1962) had brought severe storm surges to Hong Kong, causing heavy casualties and damages. FIGURE 21 Projected changes in the mean sea level in Hong Kong and its adjacent waters under different greenhouse gas concentration scenarios relative to 1986-2005 Mean sea level expected to rise further m 1.2 High 1.0 Medium-high Medium-low Low 0.8 Damages to ships and piers at Central, Hong Kong Island, brought by severe storm surge during the great typhoon of 1874. Sea waves bombarding the coast of Central, Hong Kong Island, during the great typhoon of 1906 which caused a death toll of more than 10,000. 0.6 10-year average sea level change 0.4 likely range for 2091-2100 0.2 0 2000 2010 2020 Observed High Medium-high 2030 2040 2050 2060 2070 2080 2090 2100 year Medium-low Low With a warming climate, the mean sea level in Hong Kong and its adjacent waters is expected to continue rising for the rest of the 21st century, and the threat of storm surges brought by tropical cyclones will correspondingly increase. A sea level of 3.5 m that can cause serious flooding in certain low-lying areas in Hong Kong, such as the one brought by Typhoon Hagupit in 2008, is a 1-in-50 year event today. It would however become a 1-in-5 year to 1-in-10 year event by 20212040 and an annual event by the end of the 21st century if the high ends of the sea level rise projections materialize. Projection data of mean sea level in Hong Kong: The threat of storm surges brought by tropical cyclones will increase with rising sea level. Severe flooding in Tai O during the passage of Typhoon Hagupit in 2008 18 Storm surge damages by Typhoon Wanda in 1962: 19 HONG KONG HONG KONG Storm surge and high waves caused by tropical cyclone Mean Sea Level Chart Datum Increased threat of storm surges with a higher mean sea level Mean Sea Level 1O Mitigating climate change – our role and responsibilities Just as mankind has played an undeniable role in bringing about climate change, we have an inescapable responsibility in mitigating the impact so caused. While some of the changes that are already taking place may not be reversible, the scenario-based projections as described in IPCC AR5 do provide some hope for steering the future course of events and hence mitigating the overall impact to a certain extent. FIGURE 22 Greenhouse gas emissions in Hong Kong by sector in 2012 Electricity generation is the major source of emissions. 68.2% Total Chart Datum 43.1 MILLION TONNES 17.1% Electricity generation Transport CO2 equivalent 5.4% 3.9% 0.1% 5.3% Waste Other end use of fuel Industrial processes and product use Agriculture, forestry and other land use 20 21 HONG KONG HONG KONG 11 Adapting to climate change – be prepared Global temperature rise by the end of the 21st century is likely to be around 3ºC (relative to pre-industrial levels) even with full implementation of COP21 countries’ pledges. While we should make every effort to reduce greenhouse gas emissions, we also need to be prepared for the impacts of a warmer world, such as more extreme heat, more extreme rainfall and higher sea level. Save energy and water Use energy-efficient products and switch them off when not needed Adopt a low-carbon and pro-green lifestyle FIGURE 23 Integrating thermal load and wind information in urban planning Drive less and drive smart Reduce waste and recycle Whatever the governments of this world pledged in COP21, ultimately it is down to us as citizens of the planet to achieve the targets set through a change in mindset, lifestyle and consumption behaviour. And we need to act conscientiously, collectively and with urgency. We should also spread the word around, promote such awareness among the younger generations, and pursue societal actions in support of sustainable efforts in meeting the long-running challenges of climate change. Energy saving tips: 22 Water saving tips: 23 HONG KONG HONG KONG FIGURE 24 Building infrastructure to reduce urban flood risk during heavy rain events 12 Collaborative effort in combating climate change The Hong Kong Observatory supports the Global Framework for Climate Services – an international initiative launched by the World Meteorological Organization to enhance and extend the effective use of scientificallybased climate information to cope with climate variability and climate change in the five priority areas of energy, agriculture and food security, water, health and disaster risk reduction. The Observatory has been collaborating with partners and stakeholders in such efforts over a wide range of issues: With government bureaux and departments to promote public awareness of climate change Constructing check dam to prevent debris flow Strengthening coastal protection 24 With Radio Television Hong Kong to spread the messages about climate change With the utility sector to encourage behavioural changes in mitigating climate change With the academia in conducting climate research Production of videos on tropical cyclone hazards which were shown at the Third United Nations World Conference on Disaster Risk Reduction at Sendai, Japan in 2015: With Education Bureau to produce special educational television programmes on climate change Projection of rainfall and Standardized Precipitation Index submitted to the Hong Kong/Guangdong Joint Liaison Group on Combating Climate Change: 25 HONG KONG HONG KONG The Observatory provides scientific input to climate change documents in Hong Kong, such as the Hong Kong Climate Change Report 2015 and Hong Kong Climate Resilience Roadmap for Business, and actively supports the policies and actions in climate mitigation, adaptation and resilience undertaken and coordinated by the government's high-level Steering Committee on Climate Change. The Observatory facilitates stakeholders and decision-makers in the planning and implementation of adaptation measures based on the latest assessment of climate trends and projections. In view of the likelihood of more frequent extreme weather as a result of climate change, the Observatory through its forecasting and warning services, as well as its public education activities in collaboration with partners on specific issues such as landslips and urban flooding, also contributes to disaster risk reduction efforts to enhance the community’s preparedness and resilience against the threats of natural The Observatory actively supports hazards. Such collaboration extends to the policies and actions in climate school talks and other outreach initiatives on thematic topics such as energy saving and and biodiversity conservation for the mitigation of climate change. mitigation, adaptation resilience. Useful links • Hong Kong Observatory Climate Change Webpage www.weather.gov.hk/climate_change/climate_change_e.htm • The Fifth Assessment Report of IPCC Working Group I www.ipcc.ch/report/ar5/wg1 • Environmental Protection Department Climate Change Webpage www.epd.gov.hk/epd/english/climate_change • Council for Sustainable Development www.susdev.gov.hk/html/en/council • Environmental Campaign Committee www.ecc.org.hk/english/index.html • The 21st Conference of the Parties to the United Nations Framework Convention on Climate Change www.cop21.gouv.fr/en Joint school talks with partners Director of the Observatory giving a speech at the launch of the Hong Kong Climate Change Report 2015 Production of YouTube videos to promote public awareness 26 Hong Kong Climate Change Report 2015: Hong Kong Climate Resilience Roadmap for Business: 27 HONG KONG Appendix Source of figures and data FIGURE 25 Projected annual mean surface temperature change from the period 1986-2005 to 2081-2100 under the low (upper left), medium-low (upper right), medium-high (lower left) and high (lower right) greenhouse gas concentration scenarios. Figure 1: World Meteorological Organization Figures 2, 5, 8-12, 25 and Table 1: Intergovernmental Panel on Climate Change Figure 3: A Reconstruction of Regional and Global Temperature for the Past 11,300 Years. Shaun A. Marcott et al. Science 339, 1198 (2013); DOI: 10.1126/science.1228026. Figures 4 and 6: US National Aeronautics and Space Administration Figure 7: Global Carbon Project Figures 13-21: Hong Kong Observatory Figure 22: Data from Environmental Protection Department Figure 23: Planning Department Figure 24: Environment Bureau Photo credits TABLE 1 Projected changes in global mean surface temperature and global mean sea level rise for the mid- and late 21st century under different greenhouse gas concentration scenarios relative to 1986-2005 2046-2065 Global mean surface temperature change (ºC) Greenhouse gas concentration scenario Low Medium-low Medium-high High Global mean sea level rise (m) 28 Greenhouse gas concentration scenario Low Medium-low Medium-high High U. W. O. Field, B. F. Molnia, US National Snow and Ice Data Center (Melting of Muir Glacier, Alaska's Glacier Bay from 1941 to 2004) P.5 Mark C. Olsen, US Air Force (Storm surge caused by Hurricane Sandy along the east coast of the United States in 2012) P.6 weibo.com/szmb (Heavy rain in Shenzhen on 11 May 2014) P.7 The secretariat of the United Nations Framework Convention on Climate Change (COP21, Paris) P.19 Mr Shun Chi-ming (Damages to ships and piers at Central, Hong Kong Island, brought by severe storm surge during the great typhoon of 1874. Sea waves bombarding the coast of Central, Hong Kong Island, during the great typhoon of 1906 which caused a death toll of more than 10,000.) P.19 Television Broadcasts Limited (Severe flooding in Tai O during the passage of Typhoon Hagupit in 2008) P.24 Civil Engineering and Development Department (Constructing check dam to prevent debris flow. Strengthening coastal protection.) P.25 Radio Television Hong Kong (Poster of “Meteorology Series IV”) 2081-2100 Mean Likely range Mean Likely range 1.0 1.4 1.3 2.0 0.4 - 1.6 0.9 - 2.0 0.8 - 1.8 1.4 - 2.6 1.0 1.8 2.2 3.7 0.3 - 1.7 1.1 - 2.6 1.4 - 3.1 2.6 - 4.8 2046-2065 P.4 2081-2100 Mean Likely range Mean Likely range 0.24 0.26 0.25 0.30 0.17 - 0.32 0.19 - 0.33 0.18 - 0.32 0.22 - 0.38 0.40 0.47 0.48 0.63 0.26 - 0.55 0.32 - 0.63 0.33 - 0.63 0.45 - 0.82 29 Published by the Hong Kong Observatory The Government of the Hong Kong Special Administrative Region Printed on 100% recycled paper