Climate and Weather
Weather and climate are driving forces for northern ecosystems. Weather influences our environment every season, every year. One extreme weather event can affect wildlife or habitats for many years. Climate is the average of weather over a long time.
Weather and climate are directly related to changes in northern ecosystems, including changes in wildlife habitat, changes in species composition and changes in forest fire patterns.
Indicators on observed weather and climate trends can be compared with trends predicted by climate change models to help us adjust these predictions for the future.
3.1. Trends in observed seasonal weather compared to normal
This indicator tracks the differences, called “departures”, in temperature and precipitation from normal values measured for each season.
Normal values are the average observed temperatures and precipitation from 1961-1990. Departures are differences from this normal measured in degree Celsius for temperatures, and in % for precipitation. Seasons are defined as spring (March, April, May), summer (June, July, August), fall (September, October, November) and winter (December, January, February).
The information is organized in two climate regions: the Mackenzie District, including all forested NWT, and the Arctic Tundra, covering all tundra ecozones in the NWT as well as most of Nunavut and northern Quebec.
Canadian Climatic Regions – Forested NWT is called the Mackenzie District and NWT’s Arctic is included in the larger Arctic Tundra region. Map courtesy of © Environment Canada, Climate Research Division.
Information for this indicator is obtained from the Climate Trends and Variations Bulletin published every season by the Climate Research Division of Environment Canada. Interpretation of climate trends are provided by the Climate Research Division, based on a study produced for Canada's Ecosystems Status and Trends Report . Quotes from that report and from the web-based Bulletin were noted. Additional interpretation specific to each graph for NWT was provided by ENR. Details on changes in analysis provided by Bob Whitewood, Climatologist, Climate Data and Analysis Section Climate Research Division, Science and Technology Brand, Environment Canada.
NWT Focus
This indicator presents a series of snapshots of NWT’s seasonal weather and compares them to what was measured as normal (average) between 1961-1990. Some weather events or large departures from normal can be used to analyze weather effects on wildlife, habitat disturbances such as fires or floods, and the ability of people to travel or use renewable resources. The variable weather and extreme climate of the NWT are part of our environment. This indicator tells us how this variability is changing or becoming unpredictable.
Current view: status and trend
Temperature
Temperature departures from normal vary greatly between years in the NWT (see Natural Climate Fluctuations Focal Point). In addition to these large fluctuations, temperatures in the past 15 years have been in general warmer in all seasons than during the 1950-1980. The warmest summer on record for both the Mackenzie District and the Arctic Tundra was during the strong El Niño event in 1998.
Warming temperature are most notable in winter in both the Mackenzie District and the Arctic Tundra regions. The warmest winter ever recorded in the Mackenzie District was in 2005/2006 and in 2009/2010 in the Arctic Tundra3. Normal climatic variations could not explain this warm winter, for example, an El Niño event was not occurring during that year (see Natural Climate Fluctuations Focal Point).
The Inuvialuit people have noticed ‘higher temperature and winter lows not as extreme” in the Inuvialuit Settlement Area4, Southern and Northern Arctic.
Spring
Spring temperatures are variable with a trend towards warmer weather and more variability in the last 10 years in both the Mackenzie District and the Arctic Tundra. The warmest spring on record across the NWT was in 2010.
Summer
Summers, in general, have shifted to warmer than normal temperatures during the past 15 years in both the Mackenzie District and the Arctic Tundra.
Fall
Fall temperatures are highly variable, but in general have been warmer than normal for the past 15 years in both the Mackenzie District and the Arctic Tundra.
Winter
Highest increase in winter temperature in all of Canada is occuring in the Mackenzie District. The temperature increased by 4.5 C between 1948 and 2011. Overall, there is trend towards warmer weather in the winter in the Arctic Tundra for the past 15 years.
Precipitation
Precipitation varies greatly between years across NWT’s climatic regions. The greatest departures from normal occurred during winter in the Arctic Tundra, where snowfall has increased by about 20-40%. This snow may not remain on the ground of as long as before: the Inuvialuit people have noticed the precipitation is harder to predict, and have noted that there is less snow on the ground, for less long. They have also noticed more freezing rain in the winter in the Southern Arctic (Inuvik and Paulatuk)4.
Precipitation in the Mackenzie District is highly variable (see NATURAL CLIMATE FLUCTUATIONS Focal Point). In contrast to the Arctic Tundra, winter snowfall in the Mackenzie District appears to be declining. This fits with what climate change models have predicted (see THE BIG PICTURE: A CHANGING PLANET Focal Point).
Winter
Snowfall in the Mackenzie District is highly variable. The driest winter on record for the Mackenzie District occurred in winter 2009/2010. Snowfall in the Arctic Tundra is increasing noticeably.
Spring
Springs had been wetter than normal during the past 20 years, but have been drier for the past two years. In 2011, the Mackenzie District experienced its direst spring on record: precipitation was 49% below normal.
Summer
Summer precipitation is highly variable, especially in the Mackenzie District. Summer rains in the Arctic Tundra have been slightly above normal.
Fall
Fall rain and snow in the Mackenzie District is highly variable but near normal. Fall rain and snowfall in the Arctic Tundra are increasing.
Spring 2011 was the direst on record in much of the NWT.3 Source: Climate Research Division. Environment Canada.
Looking forward
Both climate regions of the NWT are warming up - in every season. This is occurring in addition to the large annual and decadal fluctuations in weather that are normal. Exceptionally warm winters like 2005/06 should be expected in the future. Observed changes in both temperature and precipitation in the Arctic have been larger than what is expected from natural climate variations, and are consistent with what is predicted from climate changes due to increased greenhouse gas emissions11, 16.
Example of changes in winter snows. In winter, some High Arctic islands experienced more snow compared to 1950-803. Source: Climate Research Division, Environment Canada.
The Arctic Tundra is becoming snowier in winter. In addition, precipitation (wet snow or freezing rain) in both fall and spring has increased in the Arctic Tundra. Snow accumulation in that region is normally very small. For example, normal snow depth in Sachs Harbour, NT is only 8-14 cm7. It’s important to monitor changes in precipitation because rain on snow in fall or spring have been linked to increased mortality in Peary Caribou and Muskox populations on the High Arctic islands (see Species at Risk Focal Point). More variable and unpredictable weather is a serious concern for all Inuvialuit communities4.
Looking around
Trends in temperatures in winter from 1950-2007. Source: Climate Research Division of Environment Canada.
The strongest winter warming has occurred in western Canada, in particular in the Taiga Plains. The increase in winter temperature in the North is so pronounced that it drives the national averages. These increases fit with model predictions of global climate changes due to human emissions of greenhouse gases16.
Find out more
Other focal points
Technical note
The reference normals were estimated for the period 1951-1980 in the SOE report in 2009 and 2010. These were revised by the CRD to 1961-1990, the standard used by the World Meteorological Organization. Temperature and precipitation data have been re-calculated starting wit the winter 2010-2011 Bulletin. There have been several changes to the data which does, in some cases, change the results of the calculations. First, more stations are used for the analysis (from 131 stations for the old CTVB to 470 stations in the new version for precipitation). Second, the reference period has changed. Third, adjustments for precipitation measurement errors is improved, as well as homogenization procedure for temperature. Fourth, a statistical procedure called "gridding" was applied to station values to get a more even representation for regional values.
3.2 Trends in length of growing season and snow season
This indicator tracks two important climatic drivers of ecosystem change: the length of the growing season and the length of snow cover season.
The start of the growing season is defined as the date when mean temperatures are greater than 5 C over 5 consecutive days in spring and the end of the growing season is when the inverse condition occurs16. The snow cover duration is the number of days with 2 cm or more of snow on the ground.
The information is presented by ecozones analysed by climate experts at the Climate Research Division, Environment Canada as a study16 produced for Canada’s Ecosystems Status and Trends16 Report.
NWT Focus
Summers in the NWT are short but intense with sunlight. The number of days with snow cover also affects how wildlife and humans respond to our changing winters. Many NWT species have adapted to short intense summers and long periods of snow cover by migrating, hibernating or changing behaviour and food sources to optimize survival and reproduction. Changes in the growing and snow seasons may have an impact on wildlife behavior, and ultimately on their distribution and survival. Species previously not capable of surviving in our ecosystems may find new habitats in the NWT if we have less severe snow seasons and longer growing seasons. Species adapted to cold may show population declines. The effects of changes in both the growing and snow seasons on wildlife can be tracked using this indicator as studies become available.
Current view: status and trend
Overall, spring is arriving earlier, lengthening the growing season and shortening the snow season. It remains unclear if this is occurring in every ecozone as no data is available for some analyses and the length of the data record may not be long enough yet to detect some changes.
| Ecozone |
Growing Season* |
Snow Season** |
| Arctic |
No change |
Shorter by 5.1 days in Spring |
| Taiga Shield West |
No change in length but an earlier growing season is noted (by 11 days) |
? |
| Taiga Plains |
Longer by 9 days |
Shorter by 12.3 days in Spring |
| Taiga Cordillera |
Longer by 28 days |
? |
* Only significant changes are reported over the period from 1950-2007. Based on only 5 weather stations.
** Only significant changes are reported over the period from 1950-2006.
? There is no data records long enough to analyze trends for these ecozones. West: western portion only, excluding the Quebec section.
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Warming, Permafrost, and Tundra Vegetation
Warming effects on permafrost in the Southern Arctic (near the Mackenzie Delta) is presented in the Permafrost focal point. Permafrost is degrading and altering vegetation by creating disturbed areas that are nutrient rich, enhancing growth of green alders. Thaw slumps resulting from permafrost degradation are increasing9 and can accelerate the effects of climate change on tundra vegetation10.
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Degrading permafrost increases slumping, which results in changes in tundra vegetation, including more shrubs. © GNWT/D Downing |
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Warm winters and Parasites
Warming is changing the ecology of parasites already in the North, and is facilitating invasion of new parasites from elsewhere8. See the Wildlife focal point for more details on parasites in Dall’s sheeps.
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A nematode was recently discovered in Dall’s sheep in the NWT (2001). A climate-parasite model predicts that with climate warming areas further north would be suitable for more types of parasites8. The effects of changes in parasites and disease loads in northern wildlife need to be monitored. © GNWT/A Veitch |
Winter icing and Peary Caribou
The effects of changes in precipitation, rain events on snow, in the high Arctic on Peary Caribou5 are presented in the Species at Risk focal point. |
Peary Caribou populations can decline dramatically during icing events that prevent access to their food in winter © Banks Island Peary Caribou GNWT/J. Nagy |
Sea ice decline and Polar Bear
Reductions in sea ice in the southern Beaufort sea are linked to increasing proportion of the polar bear population coming on land during the fall open-water period and an increase in the amount of time individual bears spend on land8. Declining polar population in the southern Beaufort Sea can be linked to sea ice declines in this area. It is expected that the Northern Beaufort sea population may not decline in the short term as sea ice there is not changing6. More details are presented in the Species at risk focal point. |
Polar Bear in the southern Beaufort Sea © Courtesy of CASES |
Longer fire season but no trends in the number and extant of fires
Trends in forest fires are presented in the Vegetation focal point. By the 1990s onwards more fires are occurring in early spring and late summer compared to the 1960s. This change in the extent of the “fire season” is partly due to changes in climate. In the NWT, the number of fires and the area burned each year are variable, and increased in the 1990s, but decreased in the 2000s. Climate change models are predicting an increase in forest fires in the next decades. |
Forest fires in the Taiga Plains, NWT in July 2005. © D Downing/GNWT |
Species moving north
Trends in movements of mammals are presented in the Wildlife focal point. As well, some species of birds that are common further south are extending their range in the NWT. The best known of these range extension is for the Black-billed Magpie. This species is now found as far north as in the Sahtu, surviving our winters there15. A warming winter climate best explain these rapid range extensions. Winter warming is also linked to the rapid range extension of some forest pest, such as the Mountain Pine Beetle12,2, a species not present yet in the NWT, but closely monitored by ENR. Trends in forest pests are presented in the Vegetation focal point. |
Black-billed Magpie © G Court |
A climate mismatch
A mismatch between breeding and availability of food for some species of migratory birds nesting in the Arctic and boreal forest is thought to be the main cause of their decline in populations13.
“…a dependence on photoperiod as a breeding cue could limit the ability of Lesser scaup … to adjust timing of nest initiation with changes in climate and invertebrate phenology”
Quote from: DeVink et al. 2008. Auk (125).
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Lesser Scaup male and female in the Taiga Shield © J. Nagy |
Looking around
These changes are predicted by climate change scenarios and are part a trend toward spring warming and earlier snow melt observed in the northern hemisphere1, 16.
Looking forward
The rate of change in temperature and precipitation is faster than what climate change models have predicted. Normal climatic variations do not fully explain these warming winters and changes in precipitation. There is evidence that natural climate fluctuations, such El Nino, enhances the effects of continued warming in the Arctic causing, some years, rapid and less predictable changes in northern ecosystems, such as a record low in Arctic sea ice in September 2007.
Find out more
Climate Research Division, Environment Canada at www.cccsn.ca.
Technical notes
The selection of 5 °C as the minimum temperature requirement for the growing season is arbitrary. The actual growing season is different for different plant species. The relative changes in the start, end and length of the growing season, however, are relevant to all species and ecosystems16. Trends are statistically significant at 5% level. See Climate Research Division study for details in statistical procedures16. The trend analyses are based on weather stations in the entire ecozone in Canada, including some in the NWT. The number of stations used for analysis are, for each ecozone, for growing season (gs) and snow season (Snow): Arctic: 20 (gs); 26 (snow), Taiga Shield West: 5 (gs); 0 (snow), Taiga Plains: 6 (gs), 11 (snow); Taiga Cordillera: 1 (gs), 0 (snow).
Other focal points
NATURAL CLIMATE FLUCTUATIONS
THE BIG PICUTRE: A CHANGING PLANET
Reference List
Ref 1- Arctic Council. 2004. Arctic Climate Impact Assessment.
Ref 2 - Canadian Forest Service. 2008. Forest forward - Moving beyond the pine beetle. Natural Resources Canada.
Ref 3 - Climate Research Division. 2009. Climate Trends and Variations Bulletin. Environment Canada Webpage. Environment Canada.
Ref 4 - Communities of Aklavik et al. 2005. Unikkaaqatigiit – Putting the Human Face on Climate Change: Perspectives from the Inuvialuit Settlement Region. Joint publication of Inuit Tapiriit Kanatami, Nasivvik Centre for Inuit Health and Changing Environments at Université Laval and the Ajunnginiq Centre at the National Aboriginal Health Organization. Ottawa.
Ref 5 - COSEWIC. 2004, COSEWIC assessment and update status report on the Peary caribou Rangifer trandus pearyi and the barren-ground caribou Rangifer tarandus groenlandicus (Dolphin and Union population) in Canada. Ottawa.
Ref 6 - COSEWIC. 2008, COSEWIC assessment of update status report on the Polar Bear Ursus maritimus in Canada, Ottawa.
Ref 7 - Environment Canada. 2008. Canadian Climate Normals 1971-2000 - Sachs Harbour, NWT. Climate Normals & Averages, Canadian Daily Climate Data (CDCD).
Ref 8 - Kutz, S. et al. 2009. The Arctic as a model for anticipating, preventing, and mitigating climate change impacts on host-parasite interactions. Veterinary Parasitology, 163: 217-228.
Ref 9 - Lantz TC and Kokelj SV, 2008, Increasing rates of retrogressive thaw slump activity in the Mackenzie Delta region, N.W.T. Canada. Geophysical Research Letters, 35:L06502.
Ref 10 - Lantz, T. C., Kokelj, S. V., Gergel, S. E., and Henry, G. H. R. 2009. Relative impacts of disturbance and temperature: persistent changes in microenvironment and vegetaion in retrogressive thaw slumps. Global Change Biology, 15:1664- 1675.
Ref 11 - Min, S.-K., Zhang, X., and Zwiers, F. 2008 Human-induced Arctic Moistening. Science, 320:518- 520.
Ref 12 - Robertson, C., Nelson, T. A. Jelinski D. E., Wulder, M. A., and Boots, B. 2009. Spatial-temporal analysis of species range expansion: the case of the mountian pine beetle, Dendroctonus ponderosae. Journal of Biogeography, 36:1446- 1458.
Ref 13 - Tulp, I. and Schekkerman, H. 2008. Has Prey Availability for Arctic Birds Advanced with Climate Change? Hindcasting the Abundance of Tundra Arthropods Using Weather and Seasonal Variation. Arctic, 61:48-60
Ref 14 - Whitewood B. E-mail to Carriere, S. 2011. RE: Data on the Climate Trends and Variations Bulletin.
Ref 15 - Working Group on General Status of NWT Species. 2011. NWT Species Infobase 2011 Version. Yellowknife. GNWT.
Ref 16 - Zhang, X. et al. 2008. Canadian Climate Trends Ecosystem Status and Trends Report. Report for ESTR, Climate Research Division. Environment Canada.