Climate Impacts in the Pacific Northwest What is Climate?faculty.washington.edu/wgold/bis358/022008.pdfClimate Variability: Comparing ENSO and PDO z In Seattle, we observe similar

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Climate Impacts in the Pacific Northwest

www.alaskakenairiverfishing.com

http://users.owt.com/chubbard/gcdam/

Justin MinderSandra Penny

What is Climate?

“Climate is what you expect Weather is what you get”

• Weather: Characteristics of the atmosphere over a short period of time, usually no more than a few days.

• Examples: Current Temperature, Rainfall, Humidity, Solar radiation

• Climate: The statistics (eg. average) of weather over a long period of time.

• Examples: Average Temperature, Rainfall, Humidity, Solar radiation

ClimateWeather

Source: www-k12.atmos.washington.edu/k12/grayskies/

Climate Change v. Climate Variability

We see the sum of both

Climate variability (i.e. Natural swings)

Climate change (e.g. warming trend)

Time (years)

"clim

ate"

Puget Sound Area Air

Temperature

Sea Surface Temperature

(Race Rocks lighthouse, Victoria)

This is very similar to what we observe in our region:•What a mess!

•Natural variations nearly overwhelm climate change (for now).

... but there is some hope:

Variations in PNW are strongly shaped by two large-scale patterns…

Climate Change and Climate Variability

Source: UW Climate Impacts Group

Climate Variability:ENSO - El Nino Southern Oscillation

•year to year variations are often related to ENSO.

•El Nino = warm/dry winters. •La Nina = cold/wet winters.

•Effects of ENSO can be seen globally

•The origins of ENSO and its most striking effects are farther to the south, near the equatorial Pacific.

Strong El Nino year

Strong La Nina year

Source:


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Climate Variability:PDO - Pacific Decadal Oscillation

Warm PDO phase

Cool PDO phase

•decade to decade variations are often related to the PDO.

•Warm PDO = warm/dry winters. •Cool PDO = cold/wet winters.

•Again, effects are felt over a really large area. This time, the pattern looks a little bit different.

Source:

UW Climate Impacts Group

Source:


Climate Variability:Comparing ENSO and PDO

In Seattle, we observe similar effects of PDO and ENSO.Even with perfect predictions of ENSO and PDO, about 70% of the region’s winter climate is unexplained (life is messy).Often we use these modern climate variations as an analog for future and past climates.


Puget Sound Area Air

Temperature

Sea Surface Temperature

(Race Rocks lighthouse, Victoria)

This is very similar to what we observe:

In the PNW, natural variations nearly overwhelm global warming(for now).

What a mess!

Climate Change and Climate Variability

... but there is some hope:

Climate models help us understand the trends and changes in PNW climate


Average Northwest warming (predicted), 2000-2100•Using several different GCMs with different emission scenarios, we get a global prediction of the world’s temperature in 100 years.

•PNW warming is predicted by looking at a small region in the GCM output.

uncertainty

Cha

nge

in a

vera

ge te

mpe

ratu

re (F

)

Climate Change in the PNW:Projections from global models

Source: Mote, Salathé and Peacock 2005

Time (yrs)

Projected changes in the Pacific Storm Track

Climate Change in the PNW:Regional Effects of Global Warming

Current wintertime rainfall (1950-2000)

Projected wintertime rainfall under global warming (2050-2100)

Storm track moves a bit north and gets wetter

Source: Salathe 2006

Comparing Climate Change and Variability in the PNW

• Currently, average annual temperature only fluctuates by a few degrees from one year to the next.

• By 2100 (and maybe 2050), an “average year” will be warmer than the warmest years today.

uncertainty

– Currently, average annual precipitation can vary from 20-35” in one year.

– By 2100, an “average year” will resemble a fairly wet winter today.


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The details of the terrain, and land-water contrasts be very important in shaping the climate...particularly over the PNW

These effects are not resolved by Global Climate Models (GCMs)

There are two main ways that scientists “downscale” global climate projectionsStatistical methods use relationships we observe to hold now (e.g. between

elevation and temp) to downscale GCM info... but for it to work the relationships must not change

Dynamical methods use model inside a model to run detailed simulations of future climate just over the region of interest


Source: Eric Salathe,



Results of downscaling suggest :

− Autumn rain increases even more than expected from GCMs over the mountains

(due to circulation changes) − Where snow melts extra warming occurs in the

winter and spring(due to snow-albedo feedback)

− Springtime cloudiness increases over Western Washington possibly mitigating some of the warming.

(due to stronger winds blowing off the ocean)

Climate Impacts in the PNWMajor systems affected by climate change and

variability

Water resources

ForestsSalmon

www.alaskakenairiverfishing.com

Coastlines

Some impacts are near certain, others are anybody's guess

What we know well:Temperature will increase. Total wintertime precipitation will likely increase, but probably not as drastically.

We know quite a bit about factors that strongly depend on temperature. Somewhat less about those that depend on precipitation:Snow pack, likelihood of intense precipitation events, summer water supply, snowfall in the passes, coastal flooding, winter flooding in rain dominated basins,

We can only make educated guesses about the rest, since they depend on much more than just average temperature and precipitation:Invasion of exotic species, changes in ecosystem, effects on wildlife and salmon, water quality, forest productivity, forest areal extent, coastal erosion, landslides, annual streamflow volume, wind storms

Climate Impacts on:Water Resources

It is already a challenge to balance the needs of all the parties with claims to water in the Columbia basin, and it requires bringing together international, tribal, federal, state, and local entities

Population growth in future decades will make the challenges even greater

Many key systems in the region depend critically on runoff:Hydropower (~70% of our power)IrrigationSalmonRecreationFlood ControlNavigationDrinking water...

http://users.owt.com/chubbard/gcdam/

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The PNW is wet-winter, dry-summer region

To meet water demands in the summer, we rely on storage from the previous winter

Dams help, but only so much (limited capacity, must be emptied to protect against floods)

Our current water management system depends on the storage of winter precipitation as snowpack

Source: Mote et al. 1999

Time (year)

Stre

amflo

w

Blue dots = Neg ENSO (cold-wet)Red dots = Pos ENSO (warm-dry)Lines = averages for +/- PDO

Time (month)

Stre

amflo

w


Natural Variability (PDO and ENSO)

Snowpack at Snoqualmie Pass

Time (month/day)

Sno

wpa

ck


Bales, et al. 2006

falling between 0 and -3 C


Sensitivity of snowpack to warming

Mote (2006)

Temperature-related trends in snowpack

red=lossblue=gain

Source: Mote 2005, BAMS

Difference in Snowpack1990s-2050s(Apr 5)


Projected changes in snowpack

Climate Impacts on:Water Resources Projected changes in water supplies

today

2040s


Climate Impacts on:Ski Industry

Snow model simulations by the UW Climate Impacts Group show that average ski conditions at Snoqualmie Pass (3000 ft), could change dramatically by 2025. The likelihood of opening by Dec. 1 could decline by 50%Average season length could decline by 28%The likelihood of rain when the ski area is open could increase by 25%.

The changes in snow conditions by 2025 are less pronounced for Stevens Pass (4050 ft)

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Climate impacts on: Forests

Timber industry in the Pacific Northwest contributes significantly to the economy

Forest also offer habitat to a range of species

Some forests / species respond directly to variations in climate (e.g. PDO)

...but many species show no direct climate sensitivity

warm-dry

cool-wet


− However, climate also can control the occurrence of “high intensity disturbances”...

Fires PestsPathogensWindstorms


− Climate variability (the PDO) exerts control on the amount of area burned

− Under global warming, hotter summers, with more evapo-transpiration, may increase fire hazard



Photo credit: Don Hanley

Photo credit: Don Hanley

The mountain pine beetle is a pest that can devastate forests

...and it cares about climate:

It dies when it gets too cold (-40 C)

If it gets warm enough (15.5 C) it can fly and spread

It more readily destroys stressed forests (e.g. Those suffering from d ht)

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Climate impacts on: ForestsMountain Pine Beetle Outbreaks

Source: Source:

•Salmon catches over the last 70 years tend to be correlated with the PDO

•In a warmer world, some species will be positively affected, and some negatively affected.

Climate impacts on: Salmon

Salmon and Climate Variability (PDO)

Cold-wet

Warm-dry

Cold-wet

Warm-dry

Source: Mantua, 1999

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Climate impacts on: SalmonEffects of climate change on salmon are uncertain and diverse

Source: Mote ca. 2005

winter flooding

low summer streamflow; higher temp.

changing estuary conditions (prey,

predators, competitors)

possible effects still unknown

Can guard against impacts by maintaining diverse ecosystems!

Coastal impacts: Sea level rise

Regional sea level rise depends on four things:• Global sea level rise• Local tectonics • Isostatic rebound• Changes in atmospheric

circulation patterns Observed global sea level rise:

Source: IPCC TAR 2007


Regional sea level rise depends on four things:• Global sea level rise• Local tectonics • Isostatic rebound• Changes in atmospheric circulation patterns

•Tectonic plates are colliding beneath us, raising the Cascades and causing uplift in the NW Olympic peninsula

•In the last ice age, parts of Washington were covered with heavy ice, and the land is still bouncing back up.



Source: Climate Impacts Group, UW



Putting it all together

Largest uncertainties are due to unknowns in things like:

• Melting of Greenland and Antarctic ice sheets• Earthquakes• Current scientific research doesn’t agree on

whether the Puget Sound is rising or sinking• Seasonal circulation changes


Example: Chehalis river valley flooding/landslides

An extreme precipitation event:

Climate change? … or climate variability?

Intense rain is expected to get more intense under global warming....

But we can never blame a single event on climate change

Impacts of Climate on: Extreme Weather

Source: Seattle Times

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ConclusionsThe Pacific Northwest (PNW)

experiences lots of year to year variations in weather and climate, some of which can be explained by dominant patterns (PDO and ENSO)

Due to global climate change we know the PNW will get warmer (3-8 F), and winters will be wetter.

We have more uncertainties about things like extreme events, and the regional details of the changes

A variety of important systems are strongly effected by climate change and variability:

Salmon

Water resources

Forests

Coastal regions

Documents

Climate Impacts in the Pacific Northwest What is Climate?faculty.washington.edu/wgold/bis358/022008.pdfClimate Variability: Comparing ENSO and PDO z In Seattle, we observe similar