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Climate Scenarios Table

This page is part of the project: Apostle Islands

 

Scenarios for years leading up to 20401

Climate Driver Least Change Soggy Yo-Yo Hot and Bothered
Average Temperature

winter: +4 deg(F)

spring: +2 deg(F)

summer: +2 deg(F)

fall: +3 deg(F)

winter: +1 deg(F)

spring: +2 deg(F)

summer: +2 deg(F)

fall: +3 deg(F)

winter: +1 deg(F)

spring: +2 deg(F)

summer: +8 deg(F)

fall: +3 deg(F)

winter: +7 deg(F)

spring: +7 deg(F)

summer: +8 deg(F)

fall: +6 deg(F)

Hot Days No change in the number of days above 95 deg (F) or the maximum length (in days) of consecutive hot days for a given year.  Normally, there are about 0-10 "hot" days per year and the longest running period of hot days is less than 5 days.2 No change in the number of days above 95 deg (F) or the maximum length (in days) of consecutive hot days for a given year. + 5 more days each year above 95 degrees (F) and the longest running hot period is extended by 4 additional days (totaling about a week of days all above 95 each year). + 5 more days each year above 95 degrees (F) and the longest running hot period is extended by 4 additional days (totaling about a week of days all above 95 each year).
Cold Days Winter temperatures are above freezing for a total of an additional 2 weeks each year 3  Currently4 there are 150-170 cold days per year. Winter temperatures are above freezing for a total of an additional 2 weeks each year. Winter temperatures are above freezing for a total of an additional 2 weeks each year.  Extremely cold temperatures will occur more often assuming an increase in polar cold-air outbreaks from a primarily negative arctic oscillation.    Winter temperatures are above freezing for a total of an additional 3 weeks each year. 
Average Precipitation

winter: +15% change

spring: -5% change

summer: -25% change

fall: +15% change

10% corresponds to about one inch of liquid precipitation.

winter: +20% change

spring: +15% change

summer: +20% change

fall: +20% change

winter: +15% change

spring: -5% change

summer: -20% change

fall: +5% change

winter: -5% change

spring: -5% change

summer: -30% change

fall: -10% change

Precipitation Extremes  No change in heavy precipitation events.  Madeline Island experienced 26 precipitation events greater than 1" over the 1981-2010 period, so less than one event per year on average. Extreme precipitation events occur more often (3 days per year compared to once per year, historically). Extreme precipitation events occur more often (3 days per year compared to once per year, historically). No change in heavy precipitation events.
Snowfall A few additional heavy lake-effect snowfall events are projected to occur each year; Total winter snowfall is projected to decrease by about 25 centimeters per year;5 Winter precipitation is projected to increase up to 15%5 indicating more precipitation will fall as rain rather than snow Mean annual snowfall increases 15% Mean annual snowfall increases 15%   Warming winter air temperatures maintain more open surface waters on Lake Superior allowing greater amounts of lake effect snowfall to occur along the lake's southern coastline.6 However, this could compete with overall drier conditions if the AO remains positive.
Frost-free Season Increase of two weeks for frost-free days.  The growing season will likely expand more at the end of the season (fall) as opposed to the beginning (spring) based on historical trends on Madeline Island. Same as least change Greater variability from year to year with increases in the frost free season up to one month.  A long frost free season one year could be followed by a short season the next year. The frost-free season is expanded by one month (currently the season lasts 120 days on average). The timing of the frost-free season starts one week earlier and extends 3 weeks later than present.  
Wind +5% per decade +5% per decade +5% per decade Increased intensity of heavy wind events with possibility of major disturbance events.
Lake Levels

No change

Current intra-annual variability: about 1-2 feet 

Lows occur in spring (Mar/Apr)

Highs occur in late summer/early fall (Aug-Oct)

Lake Superior water levels increase up to 2 feet;7 variability remains +/- 2 feet.  Levels are now consistently 0 to +4 feet above current levels. Average lake levels are similar to present but there is greater intra- and inter-annual variability.  Levels now swing between -3 to 3 feet within current levels.

Lake Superior water levels drop 2 feet; variability remains +/- 2 feet.  Levels are now consistently 0 to -4 feet below current levels.

Lake Temperatures

Water temperatures rise 3 degrees (F) on average.

Water temperatures rise by about 1 degree (F) on average. Water temperatures are more variable from year to year.  Very cold winters will sustain colder waters for longer periods even in spite of very hot summers.  Milder/warmer winters create greater potential for increased water temperatures.

Water temperatures rise by 7 degrees (F) on average.  The length of summer stratification is projected to increase by over a month.8  Similarly, the length of the evaporation season will increase.  

Lake Ice Ice duration on Lake Superior is projected to decrease by 3 weeks Ice duration on Lake Superior decreases by 2 weeks. Great variability from year-to-year (i.e., some years lots of ice, other years little ice). Warmer winter air temperatures prevent significant ice cover from forming on Lake Superior, but ice still forms for a shorter time period in shallow, protected areas like Apostle Islands.  
Arctic Oscillation variability remains the same (i.e., the AO does not show preference for one mode over the other) The AO is more often (say, 7/10 winters) in the negative phase on average with a wavy jet stream that allows cold, moist air to dominate in the region during winter.   The AO is more often (say, 7/10 winters) in the negative phase on average with a wavy jet stream that allows cold, moist air to dominate in the region during winter.   The AO is more often (say, 7/10 winters) in the positive phase on average with the jet stream located in the far north allowing warm, dry air to dominate in the region during winter.
  • 1. The values in the table are most appropriate for the end of the time period, and earlier years will likely exhibit less change.
  • 2. Madeline Island has already experienced a relatively large increase in days over 90 deg (F), which is much more than what is projected for the larger region.  Local trends may outpace regional trends of only a small increase in hot days.
  • 3. Regional projections indicate fewer cold days in the future, but records on Madeline Island have not indicated as strong a decrease for days below 10 deg (F).
  • 4. 1980-2000 period
  • 5. a. b. calculated by taking half of the end-of-century value
  • 6. This assumes that air temperatures are cold enough to allow snow to form, which is likely the case in the near term out to 2050
  • 7. Increased annual precipitation and smaller seasonal air-water temperature gradients (decreased evaporation) will increase the net supply of water in Lake Superior.
  • 8.  calculated by taking half of the end-of-century value