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Abstract

Introduction

Methodology

Results & Discussions

Error and Uncertainty

 It is widely recognized that global average temperatures are increasing. Studies have confined that global mean surface temperatures have increased by between 0.5-1.0°F since the late 19th century.1 The 20th century's 10 warmest years all occurred after 19851 and the three warmest years on record have all occurred since 1998. Paleoclimatic reconstructions have suggested that it is warmer now then at any point in the last 100 years and the Earth has probably never warmed as fast as it has in the past 30 years.2

  The causes of this warming are disputed, but it is likely to be linked to anthropogenic sources of Carbon Dioxide released from the burning of fossil fuels. Carbon Dioxide and other gases including methane contribute to the enhanced greenhouse effect. Long wave radiation readmitted by the Earth is trapped in the troposphere, warming the lower atmosphere. 2 This is natural effect which keeps surface temperatures relatively benine. Today atmospheric CO2 levels are 370ppm compared with the constant 280ppm in the centuries leading up to the industrial revolution.3 However the evidence for a direct link is uncertain. The Earth has exhibed rapid changes in temperature many times in the past and is influenced by a number of forcing factors and feedback mechanisms,including volcanic activity and varriations in solar output. 1

 The impacts of increasing global average temperatures are as hard to predict as the degree of warming itself.While a small increase in average temperatures may not have massive implications the concern is the impacts the change will have on extreme climate events. This project uses climate data from the last 30 years to map the distribution of extreme minimum temperature across British Columbia will an aim to investigate wether increasing global temperatures have reduced the extremes of temperature recorded in the province.

Impacts of Minimum Extreme temperature: Mountain Pine Beetle

 Extreme minimum temperature can have significant impacts of the distribution of animal and plant communities. The distribution and occurrence of pest species in temperate areas are impacted by minimum extreme winter temperatures.

  Mountain Pine Beetle Dendroctonus ponderosas is a bark beetle native to British Columbia and the single most important forest pest in western Canada. 4 Adults lay their eggs under the bark of mature Lodgewood Pine trees where they spend most of their lifecycle. 5 Larvae over winter inside trees and feed on the inner bark and cut off the trees supply of waters and nutrients. The infection also introduces Bluestain fungus into the tree and a combination of the two usually kills infected trees within two or three years. 5

 

Mature Mountain Pine Beetle

Source: Natural Resources Canada

Although the beetles play an important role in natural forest ecosystems the number of infections has increased dramatically in the last 20 years; killing an estimated 300 million trees in British Columbia and damaging timber worth an estimated six billion dollars. 4. Falling winter temperatures have been cited as one of the causes of the current epidemic.

Click here for an animated map showing location ofMountain Pine Beetle outbreaks 1959-2002

 Low winter and spring temperatures are one of the main causes of mortality in Mountain Pine Beetles during the larval stage and an important population control mechanism. Although the larvae can withstand very cold temperatures for long periods, smaller or immature larvae can’t withstand temperatures lower than -40ºC and most can’t tolerant temperatures this low for prolonged periods. 4 If the preceding summer was unusually mild than low temperatures can cause beetle populations to crash.  As a result beetle distribution is limited by the -40ºC isotherm. 4 An increase in winter temperatures will expand the beetles range west and north in BC as well increasing the altitude at which the larvae can survive the winter. It is estimated that a 2.5ºC increase in average temperatures will increase the northern range of the beetle by some 7 degrees latitude. 4

Distribution of Mountain Pine Beetle Infestations

SOURCE: A. Carroll, Pacific Forestry Centre, 2001. Adapted from Safranyik, L. 1990. Temperature and insect interactions in western North America. Proceedings of the Society of American Foresters National Convention. Washington DC. SAF Publication 90-02. pp. 166-170. Isotherms from Department of Mines and Technical Surveys. 1957. Atlas of Canada.

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1. US Environment Protection Agency, 2005
   http://yosemite.epa.gov/oar/globalwarming.nsf/content/climate.html
   
2. New Scientist, 2004 http://www.newscientist.com/channel/earth/climate-change/
   
3. Intergovernmental Panel on Climate Change (IPCC) 2005http://www.ipcc.ch/
   
4. Government of British Columbia, Ministry of the Environment: Water Air and Climate Change Branch, 2002 http://wlapwww.gov.bc.ca/air/climate/indicat/beetle_id1.html
   
5. Canadian Forest Services, Natural Resources Canada, 2003 http://mpb.cfs.nrcan.gc.ca/research/index_e.html