Climate Backgrounder

Wed, 2006-04-19 09:08Richard Littlemore
Richard Littlemore's picture

Climate Backgrounder

A quick overview of the latest in international and Canadian climate research:

Background and Supplementary InformationThere is increasing unambiguous evidence of a changing climate in Canada and around the world.  Over the past century, the globally-averaged annual temperature increased by 0.6°C and the world is now warmer than at any time in at least the last 1000 years. During the century, Canadian temperatures south of the 60th parallel warmed by about 0.9°C. Over the past 50 years, during which human influences on the climate have become more obvious, Canada has warmed faster than almost any other region on the globe, with the greatest warming - more than 2oC - occurring in the MackenzieBasin.  With the exception of the southern Prairies, Canada has also become noticeably wetter. The increases in average precipitation have been accompanied by increases in both extreme precipitation and dryness in some regions. Summer Arctic sea ice has decreased in extent by 30% over the past 30 years and is projected to largely disappear by the middle of this century. Global sea level has risen 10-20 cm in the past 100 years. Future sea level rise could be much greater if there are massive ice sheet discharges from the Antarctic or Greenland, as recent evidence suggests. Higher sea-levels will enhance damage from coastal erosion and the expected increase in storm surges.The 2001 IPCC report projected that global mean temperatures will increase between 1.4 to 5.8°C from 1990 to 2100. The warming over most of Canada is projected to be substantially above that of the global average, especially during winter. These projections are based on global climate models from leading climate research groups that have tested and validated them through simulations of past and present climates.As the climate changes, there will be increasing impacts on Canada’s natural ecosystems and on its socio-economic activities. Some impacts are:
  • Inadequate water for Prairie agriculture and hydroelectric utilities due to increased drying of the continental interior and reduced snow pack and shrinking glaciers;
  • Threats to the sustainability of Canada’s natural resources due to an inability of our ecosystems to respond rapidly as the climate changes.
    • Warming allowing the spread of insects through our forests and prolonged drought making forests more susceptible to fires;
    • Warming of ocean and river waters, threatening survival of Pacific salmon, a cold water fish, by forcing it away from its spawning grounds;
  • Increasing severity and frequency of some extreme weather events, including floods and droughts, some of which are already exceeding 100-year records and requiring more robust design specifications for infrastructure;
  • Thawing of permafrost and associated effects on the human environment (infrastructure, roads, pipelines, buildings), sea ice, northern ecosystems and species, all leading to dramatic changes in the lives of northern people;
  • Increased marine traffic through the northern sea routes, increasing the likelihood of environmental impacts and challenges to Canada’s sovereignty claims in the Arctic. 
Some of these projected impacts are already detectable.Advances in climate science since the 2001 IPCC Assessment have provided more evidence supporting the need for action and development of a strategy for adaptation to projected changes.  New results include:
  • Progressive decreases in ArcticSea ice coverage in summer and winter since 1979, with record lows in 2005.  At the current rate we expect Arctic summers to be ice-free by 2050 - a state not seen on Earth for at least a million years;
  • Analyses showing that climate may be more sensitive to additional greenhouse gases than previously determined;
  • Improved understanding of the interactions between the climate system and the global carbon and sulphur cycle with the possibility that some terrestrial carbon reserves may become sources;
  • Improved understanding that a small but significant fraction (about 15-20%) of the carbon dioxide that has been released into the atmosphere by human activities (mainly fossil fuel burning) will continue to affect climate for tens of thousands of years until it is eventually neutralized through carbonate reactions in the deep ocean;
  • Confirmation that warming of the atmosphere near the surface is consistent with the projections of climate models;
  • Linking of climate change and ozone recovery (affecting ultraviolet levels in the Arctic), and the attribution of recent surface temperature change over the Antarctic to the ozone hole;
  • Identification of ocean warming to depths in excess of 700 metres and its attribution to anthropogenic (human-induced) causes. This stored heat will contribute to a continuing sea level rise for several centuries;
  • Clear demonstration that the ocean is becoming more acidic, threatening marine organisms, especially corals.
  • Identification of possible ‘tipping points’ in the carbon cycle, the North Atlantic Ocean circulation and the Greenland ice sheet, that may trigger irreversible trends with major global climatic consequences;
  • Evidence that warm Atlantic water now moves farther into the ArcticBasin and may increase the rate of sea ice melt due to warming from below.
There is an increasing urgency to act on the threat of climate change. Stopping the growth in atmospheric greenhouse gas concentrations by reducing emissions would also have benefits for air quality, human health and energy security. But since mitigation measures will become effective only after many years, adaptive strategies are essential and need to begin now.  Our climate system is dynamic and complex: further knowledge is needed of the relationships among its components, to continue to inform decisions on adapting to the inevitable impacts that we will experience.  There are several key research questions whose resolution will lead to better understanding as to how the climate will change.  For the sake of all Canadians and the global community, Canada needs a national climate change strategy to provide the best advice for action, with continued investments in research to track the rate and nature of changes, understand what is happening, to refine projections of changes induced by anthropogenic release of greenhouse gases and to analyse opportunities and threats presented by these changes.  Good policy requires good science.We would be pleased to provide a scientific briefing and further support, clarification and information at any time.

 

 

Comments

If you read the IPCC section reproduced below you will note that no positive statements are made regarding our understanding of global warming and mankind’s part in it “14.3 The Human System 14.3.1 Overview Human processes are critically linked to the climate system as contributing causes of global change, as determinants of impacts, and through responses. Representing these linkages poses perhaps the greatest challenge to modelling the total Earth system. But understanding them is essential to understanding the behaviour of the whole system and to providing useful advice to inform policy and response. Significant progress has been made, but formidable challenges remain. Human activities have altered the Earth system, and many such influences are accelerating with population growth and technological development. The use of fossil fuels and chemical fertilisers are major influences, as is the human transformation of much of the Earth’s surface in the past 300 years. Land-use change illustrates the potential complexity of linkages between human activity and major non-human components of the Earth system. The terrestrial biosphere is fundamentally modified by land clearing for agriculture, industrialisation, urbanisation, and by forest and rangeland management practices. These changes affect the atmosphere through an altered energy balance over the more intensively managed parts of the land surface, as well as through changed fluxes of water vapour, CO2, CH4 and other trace gases between soils, vegetation, and the atmosphere. Changed land use also greatly alters the fluxes of carbon, nutrients, and inorganic sediments into river systems, and consequently into oceanic coastal zones. The response of the total Earth system to these changes in anthropogenic forcing is currently not known. Sensitivity studies with altered land cover distributions in general circulation models have shown that drastic changes, such as total deforestation of all tropical or boreal forests, may lead to feedbacks in atmospheric circulation and a changed climate that would not support the original vegetation (e.g., Claussen, 1996). Regional climate simulations, on the other hand, have shown that at the continental scale, important teleconnections may exist through which more modest tropical forest clearing may cause a change in climate in undisturbed areas. Coupling the global to the local is a key challenge; regional studies may prove to be uniquely valuable. Human land-use change will continue and probably accelerate due to increasing demands for food and fibre, changes in forest and water management practices, and possibly large-scale projects to sequester carbon in forests or to produce biomass fuels. In addition, anthropogenic changes in material and energy fluxes, resulting from such activities as fossil fuel combustion and chemical fertiliser use, are expected to increase in the coming decades. Predictions of changes in the carbon and nitrogen cycles are sensitive to estimates of human activity and predictions of the impacts of these global changes must take into account human vulnerability, adaptation, and response. Predicting the future response of the Earth system to changes in climate and in parallel to changes in land use and land cover will require projections of trends in the human contributions to these global changes; this sort of modelling presents difficult challenges because of the multiple factors operating at local, regional, continental, and global levels to influence local land-use decisions. In sum, the human element probably represents the most important aspect both of the causes and effects of climate change and environmental impacts. Any policy intervention will have human activities as its immediate target.” Note in para 4 it asserts that the earth’s response is not known. Personally I think cutting down the rain forests has had a much bigger influence on things than CO2. But KYOTO does not address land mis-use at all. Mikem