Current Climate Impacts What are the effects of global warming that we have seen so far? Melting of the North Pole Why sea-ice is so important Greenland Melting Thinning of the Artic sea-ice Melting Alpine Glaciers Slowing global ocean circulation Larsen B Ice Shelf Collapses in Antarctica Ice Shelves Trends in natural disasters West Nile Virus Change in Canada References • • • • • • • • • • • •
What are the effects of global warming that we have seen so far? Drought "More intense and longer droughts have been observed over wider areas since the 1970s" (1) Cyclones & Extreme Weather "There is observational evidence for an increase of intense tropical cyclone activity in the North Atlantic since about 1970, correlated with increases of tropical sea surface temperatures." (2) "Widespread changes in extreme temperatures have been observed over the last 50 years. Cold days, cold nights and frost have become less frequent, while hot days, hot nights, and heat waves have become more frequent." (3)
Fire Hazard According to fire ecology expert Dr Kevin Tolhurst, from the new Australian Bushfire Research Centre "global warming has already started to produce more severe bushfires over recent Australian summers."(4) He says that, "much of the east coast and the southern states can look forward to more frequent and more intense bushfires". The ABC
(Australian Broadcasting Corporation) reported, "The dimensions of climate change are the subject of intense debate among scientists. But those who take a close look at exactly how climate change is measured say Dr Tolhurst's predictions appear valid." (5) Dr Kevin Tolhurst goes on to say that, "Combine that with a greater frequency of drought and more severe weather conditions, we would expect fires to not only be more intense because of the greater fuel amounts, but the likelihood of having severe fire weather conditions is likely to increase as well." (6) Melting of the North Pole The ice in the north pole has shrunk for the fourth year in a row, to "lowest extent of ice cover for more than a century"(7). This is according to scientists from the National Snow and Ice Data Center (NSIDC), Boulder, Colorado. They also warned that "the shrinkage could lead to even faster melting in coming years." (8) The data shows that since 1978 the artic ice has lost l ost 2 million square kilometres to the current are of 5.35 sq km. (9) September 1979
September 2003
‘Impacts of a Warming Arctic’ p.25 Arctic Climate Impact Assessment (ACIA) Author: Susan Joy Hassal Cartographers: Paul Grabhorn, Joshua Weybright & Clifford Grabhorn URL: http://www.acia.uaf.edu/pages/overview.html The area covered by ice in the North Pole changes with the seasons, it is usually the lowest level during September of each year. In a March 2007 article for Far North Science, climate scientists from the US National Snow and Ice Data Center, as well as scientists from the National Center for Atmospheric Research stated:-
"Given the agreement between models and observations, a transition to a seasonally ice-free Arctic Ocean as the system warms seems increasingly increasingly certain," (10) "The take home message from my perspective is that a human influence on the Arctic’s shrinking sea ice cover is a lock, and that as we continue to lose ice, we will start to see effects extending beyond beyond the Arctic," (11) "the Arctic Ocean will soon be free of ice during late summer, possibly as soon as 2040 and almost certainly by 2100". (12) Why sea-ice is so important The Arctic Climate Impact Assessment report 'Impacts of a Warming Arctic' stated: "Sea-ice covered with snow reflects about 85-90% of sunlight, while ocean water reflects just 10%. Thus, as sea ice melts, revealing more and more of the ocean beneath, the increasing absorption of solar radiation adds to global warming, which causes more melting, which in turn causes more warming, and so on…" (13) Surface Reflectivity Reflectivity
SOURCES: ‘Impacts of a Warming Arctic’ p.34 Arctic Climate Impact Assessment (ACIA) Author: Susan Joy Hassal Cartographers: Paul Grabhorn, Joshua Weybright & Clifford Grabhorn URL: http://www.acia.uaf.edu/pages/overview.html
With most of the warmth of sunlight being absorbed by land and the oceans, this increases the effects of global warming. The more ice and snow melts, the greater the effect of global warming. warming. This is seen in the diagram below. (14) Greenland Melting In a September 2006 press release by the Colorado University, Cooperative Institute for Research in Environmental Sciences stated the following: (15) "Data gathered by a pair of NASA satellites orbiting Earth show Greenland continued to lose ice mass at a significant rate through April 2006, and that the rate of loss is accelerating, according to a new University of Colorado at Boulder study." "The study indicates that from April 2004 to April 2006, Greenland was shedding ice at about two and one-half times the rate of the previous two-year period" and that the "The acceleration rate really took off in 2004".
SOURCES: Cooperative Institute for Research in Environmental Sciences (CIRES) University of Colorado
URL: http://cires.colorado.edu/science/groups/steffen/greenland/melt20 05/ CIRES Director Konrad Steffen, who has maintained more than 20 climate stations in Greenland for nearly two decades, said "temperatures have warmed by more than 4 degrees F along the western slope of its ice sheet since 1990." He went on to comment that: (16) "The increased surface melt of snow and ice provides additional meltwater to lubricate the bottom of the ice sheet and increases the ice flow velocity toward the coast," said Steffen, a CU-Boulder geography professor" "Greenland, the largest island in the world, harbors about 10 percent of the world's freshwater freshwater in its ice sheet, which is up to two miles thick in places. If the Greenland ice sheet melted completely, the world's oceans would rise more than 20 feet, according according to scientists." "Scientists believe that large amounts of freshwater purged from Greenland's eastern coast could help to weaken the counter-clockwise flow of the North Atlantic Current, lowering water and wind temperatures and potentially triggering abrupt cooling events in northern Europe." Thinning of the Artic sea-ice The weight of sea-ice pushes it down, so that most of its mass is under the surface of the water. The thickness sea-ice under the water is called the ‘draft’ and this is what scientists measure to see if there is more or less ice. Since 1958, submarines have been patrolling the North Pole. During each voyage, submarine crew measure the thickness of the sea-ice draft. (17) Scientists have evaluated this data and it shows that in the last 30 years, the average ‘draft’ or depth of the ice has decreased 40% (1.3 metres). (18) As you can see from the diagram below the readings were taken at a number of locations, over a wide area. area. While the depth of the ice in some locations reduced by less than a metre, other locations suffered much worse.
NOTE: A number of changes were made to this diagram in order to make it more easily understood; the graph showing ice loss was inverted to show depth rather the height and columns in the location map at the top were replaced with letter markers which match the graph information. For the original please click on the link below. SOURCES: D.A. Rothrock, Y. Y. Yu and G.A. Maykut, Thinning of the Arctic sea-ice cover, University of Washington, Seattle, 1999
URL: http://www.grida.no/climate/vital/30.htm Cartographer/Designer: Philippe Rekacewicz, UNEP/GRID-Arendal Melting Alpine Glaciers Glaciers are large masses of ice which form in areas of high snowfall and cool temperatures, even in summer. Glaciers are located in Antarctica, Antarctica, or at high altitudes on the slopes of large mountains (Alpine Glaciers). "A glacier is maintained by accumulation of snow at high altitudes, balanced by melting at low altitudes or discharge into the sea." (19) Alpine glaciers are particularly susceptible to shifts in climate and respond to long term changes in the Earth’s climate. As the temperature temperature of the Earth increases the melting at the base of the glacier happens faster than the speed at which it moves down the slope or valley. (20) Once a glacier has disappeared altogether, there is far less melt-water. Currently, millions of people around the world rely in part, or completely on rivers fed by glaciers. Where have all the glaciers gone?
SOURCES: ‘Where have all the glaciers Gone?’ Climate Discovery Teacher’s Guide
National Center for Atmospheric Research URL: http://www.eo.ucar.edu/educators/ClimateDiscovery/LIA_lesson4_9 .28.05.pdf Upsala Glacier, Argentina 1928 / 2004
Muir Glacier, Alaska
8 August 1941
31 September 2004
15 September 1976 8 September 2003 Slowing global ocean circulation Global ocean currents help regulate the climate in many parts of the world. Many models have suggested that these currents can be affected by global warming (There is more detail in the Future Impacts & Policy section: Melting glaciers, ice-sheets and the Global Ocean Currents)) Currents What is concerning is that changes to these currents currents will have very serious impacts around the world, especially Europe and that these changes have already started. The following is from a report from the BBC Environmental correspondent Richard Black (30 NOV 05)
Changes to ocean currents in the Atlantic may cool European weather within a few decades, scientists say. Researchers from the UK's National Oceanography Centre say currents derived from the Gulf Stream are weakening, bringing less heat north. Their conclusions, reported in the scientific journal Nature, are based on 50 years of Atlantic observations. They say that European political leaders need to plan for a future which may be cooler rather than warmer. The findings come from a British research project called Rapid, which aims to gather evidence relating to potentially fast climatic change in Europe. Atmospheric radiator The key is the Gulf Stream. After it emerges from the Caribbean, it splits in two, with one part heading north-east to Europe and the other circulating back through the tropical Atlantic. As the north-eastern branch flows, it gives off heat to the atmosphere, which in turn warms European land. "It's like a radiator giving its heat to the atmosphere," said Harry Bryden from the National Oceanography Centre (NOC) at Britain's Southampton University. "The heat it gives off is roughly equivalent to the output of a million power stations," he told reporters. By the time it reaches the northern latitudes around Greenland and Iceland, the water has cooled so much that it sinks towards the ocean floor, a process known as "overturning". This cooler water heads south,
forming the return stream of a conveyor belt. The complete cycle sees warm water coming northwards on the ocean's surface, and the cold water returning hundreds or thousands of metres underwater.
SOURCES: ‘Impacts of a Warming Arctic’ p.32 Arctic Climate Impact Assessment (ACIA) Author: Susan Joy Hassal Cartographers: Paul Grabhorn, Joshua Weybright & Clifford Grabhorn URL: http://www.acia.uaf.edu/pages/overview.html Florida-based Florida-based scientists monitor the northwards-flowing northwards-flowing Gulf Stream, Stream, and have found it has remained roughly constant over the last 50 years. The NOC researchers concentrated on the colder water flowing south; and they found that over the last half century, these currents have changed markedly. markedly. "We saw a 30% decline in the southwards flow of deep cold water," said Harry Bryden. "And so the summary is that in 2004, we have a larger circulating current [in the tropical Atlantic] and less overturning." And less heat then delivered to European shores. First evidence Computer models of climate have regularly predicted that the North Atlantic conveyor may well reduce in intensity or even turn off altogether, a concept that was pushed beyond credence in the Hollywood blockbuster The Day After Tomorrow Tomorrow.. What happens is that as Arctic ice melts and Arctic rivers flow faster trends which have both been documented - the northern oceans become less saline. Less salinity means a lower density; the waters then cannot sink, so the conveyor weakens.
Computer models have predicted that if it turned off completely, Europe would cool by perhaps four to six degrees Celsius. Commenting in Nature, Detlef Quadfasel from the University of Hamburg writes that the NOC experiments provide "...the first observational evidence that such a decrease of the oceanic overturning overturning circulation is well underway." Larsen B Ice Shelf Collapses in Antarctica The University of Colorado's National Snow and Ice Data Center using satellite imagery, "revealed "revealed that the northern section of the Larsen B ice shelf, a large floating ice mass on the eastern side of the Antarctic Peninsula, has shattered and separated from the continent. The shattered ice formed a plume of thousands of icebergs adrift in the Weddell Sea. A total of about 3,250 km2 of shelf area disintegrated in a 35-day period beginning on 31 January 2002. Over the last five years, the shelf has lost a total of 5,700 km2, and is now about 40 percent the size of its previous minimum stable extent." (21)
"This is the largest single event in a series of retreats by ice shelves in the Peninsula over the last 30 years. The retreats are attributed to a strong climate warming in the region. The rate of warming is approximately 0.5 degrees Celsius per decade, and the trend has been present since at least the late 1940s. Overall in the Peninsula, extent of seven ice shelves has declined by a total of about 13,500 km2 since 1974. This value excludes areas that would be expected to calve under stable conditions." (22) Ice Shelves The National Snow and Ice Data Center describes the formation of ice shelves; "An ice shelf is a thick slab of ice fed by glacier flow, that attaches to land along a coastline, and floats on the ocean. Ice shelves range in
thickness from about 100 to 600 meters, and some shelves last for thousands of years or longer. They fringe the continent of Antarctica, and occupy a few fjords and bays along the Greenland and Ellesmere Island coasts. At their seaward edge, ice shelves periodically periodically calve icebergs, some the size of a small U.S. state or European country." (23) "Together, an ice shelf and the glaciers feeding it form a stable system. Warmer temperatures can destabilize this system by increasing glacier flow speed and - more dramatically - by disintegrating the ice shelf. Without the shelf to slow its speed, the glacier accelerates. After the 2002 Larsen B Ice Shelf disintegration, nearby glaciers glaciers in the Antarctic Peninsula accelerated up to eight times their original speed in the next 18 months." (24) 1. Stable glacier and ice shelf
2. Two effects of warmer temperatures
3. Unstable glacier front after ice shelf 4. Glacier acceleration collapses
"While calving or disintegrating ice shelves don't raise ocean level, the resulting glacier acceleration does, and it poses a direct threat to coastal communities. More than 100 million people currently live within 1 meter of mean sea level. Greenland contains enough ice to raise sea level by 7 meters, and Antarctica holds enough ice to raise sea level by 57 meters." (25) Trends in natural disasters According to the Australian Roundtable on Climate Change;
"Globally, 37 of the 40 largest insured losses from natural catastrophes since 1970 have been weather related, as shown in Figure 2. The total economic cost of Hurricane Katrina in 2005 is estimated at US$135 billion, including up to US$45 billion insured losses." (26) Global Insured Losses from weather related natural catastrophes, 1970-2005
SOURCES: The Business Case for Early Action, April 2006 Australian Business Roundtable on Climate Change, p.14 "In Australia, 19 out of the 20 largest largest property insurance losses since 1967 have been weather related, the largest being the April 1999 Sydney hailstorm ($A2 billion in 2005 dollars). Australia is prone to bushfires, cyclones, hail, storms and flood, all of which are expected to increase in frequency and/or intensity due to climate change." (27) West Nile Virus Change in Canada "The West Nile encephalitis virus is a recent example of how far and fast a disease can spread once it becomes established in a new region. The West Nile virus can infect many bird and mammal species (including humans) and is transmitted by mosquitoes."
"It was first identified on the East Coast of North America in 1999 and spread to 43 states and six Canadian provinces by 2002. Migratory birds are responsible for its spread to other regions. Mosquitoes spread the virus to other birds (as well as to other animals and humans) within a region. Although the virus originated in tropical Africa, it has adapted to many North American mosquitoes, and so far, to over 110 species of North American bird, some of which migrate to the Arctic." "Mosquito species known to transmit the virus are also found in the Arctic. Climate has historically limited the range of some insect-borne diseases, but climate change and adaptive disease agents such as the West Nile virus tend to favor continued northerly expansion. Some arctic regions, such as the State of Alaska, have initiated West Nile virus surveillance programs."
References
1-3
Inte Interg rgov over ernm nmen enta tall Pan Panel el on on Clim Climat ate e Chan Change ge rep repor ortt 4th 4th Asse Assess ssme ment nt Report p.6: http://www.ipcc.ch/pub/spm22-01.pdf
4-6
‘Sev ‘Sever ere e bus bushf hfir ires es link linked ed to glob global al war warming ming’’ 09 DEC 03 Rafael Epstein ABC PM Radio http://www.abc.net.au/pm/content/2003/s1006755.htm
7-9
‘Ar ‘Arctic tic ice ice 'disa isappea pearing ing qui quic ckly' ly'’
28 SEP 05 Richard Black BBC News http://news.bbc.co.uk/2/hi/science/na http://news.bbc.co .uk/2/hi/science/nature/4290 ture/4290340.stm 340.stm 10 12
‘Ice-free Arctic: Not 'If' but 'When'’ 17 MAR 07 Doug O'Harra Far North Science National Snow and Ice Data Center National Center for Atmospheric Research
13 14
'Impacts of a Warming Arctic' 2004 Arctic Climate Impact Assessment http://www.acia.uaf.edu/pages/overview.html
15 16
‘Greenland Ice Sheet Still Losing Mass, Says New CU-Boulder Satellite Study’ 20 SEP 06 Cooperative Institute for Research in Environmental Sciences http://cires.colorado.edu/news/press/2006/06-09-20.html
17 18
‘Thinning of the Arctic sea-ice cover’ 1999 D.A. Rothrock, Y. Yu and G.A. Maykut University of Washington, Seattle http://www.grida.no/climate/vital/30.htm Cartographer/Designer: Philippe Rekacewicz, UNEP/GRID-Arendal
19 20
‘Where have all the glaciers Gone?’ Climate Discovery Teacher’s Guide National Center for Atmospheric Research
20 21
National Snow and Ice Data Center http://nsidc.org/iceshelves/la http://nsidc.or g/iceshelves/larsenb2002/ rsenb2002/
23 25
National Snow and Ice Data Center http://nsidc.org/sotc/iceshelves.html
26 27
'The Business Case for f or Early Action' APR 2006 Australian Roundtable on Climate Change http://www.businessroundtable.com.au/html/documents.html
