Global Warming and NW salmon

3 major questions:

1. How well do we understand the climate system and our role in changing it?

2. What might the regional impacts of global warming look like?

3. What does the answer to question 2 mean for NW salmon?

Earth’s Natural Greenhouse Effect

Some facts• Earth’s natural greenhouse effect warms

surface temperatures by ~33ºC (60 º F)• H2O vapor the most powerful greenhouse

gas (GG)• other important GG’s are CO2, CH4, N2O,

HFCs, PFCs, and SF6 …

– Human caused emissions of these GG’s are increasing the natural greenhouse effect

– Without drastic changes in current emissions trends, GG concentrations will increase dramatically in the next few centuries

Concentrations of Carbon Dioxide and Methane Have Risen Greatly Since Pre-Industrial Times

Carbon dioxide: 33% rise Methane: ~150% rise

The MetOffice. Hadley Center for Climate Prediction and Research.

• from a very long term perspective, recent CO2 changes are enormous

Long-term CO2 history

Annual Temperature Trends, (°C / century) 1901-1999

Source: P. Jones, et. al. 2000.

PNW average PNW average temperatures temperatures have risen have risen +1.5F/century+1.5F/century

Trends in April 1 snow water equivalent, 1950-2000

Trends in snowmelt runoff timing, 1948-2000

Courtesy of Dan Cayan, Scripps Institute of Oceanography and the

USGS

To appear in Climatic Change, 2003

Courtesy of Phil Mote, UW Climate Impacts GroupGeophysical Res. Letts. 2003

1928

2000

The South Cascade glacier retreated dramatically in the 20th century

Courtesy of Ed Josberger, USGS glacier group

Blue Glacier length, Olympic National Park

Looking to the future…

• “global climate system models” now used to assess the impacts of human activities on Earth’s climate– Similar to the computer models used to predict

the weather, but much more sophisticated– simulate interactions between the atmosphere,

its constituents (C02, O2, O3, N2 …), the ocean, sea ice, vegetation, and clouds

Northwest warming

7

8

9

10

11

12

13

1900s1910s1920s1930s1940s1950s1960s1970s1980s1990s2000s2010s2020s2030s2040s

Degrees C

warmest scenarioaverage coolest scenarioobserved

~1.5 to 3°Cor~ 3 to 6 °Fwarmer in the 2040’s

Most models also simulate slightly wetter winters

The main impact: less snow

Snoqualmie Pass 3022 ft

} for a ~ 4F } for a ~ 4F warmingwarming

Provided by Dennis Lettenmaier and Andy Wood, UW Civil EngineeringAccelerated Climate Prediction Initiative, a UW-SIO-PNNL collaboration

April 1st Snowpack simulations based on a low-end warming scenario

1950-99 2050’s 2090’s

Runoff patterns are temperature and elevation dependent

Oct Feb Jun

Skagit

Puyallup

Skokomish

Oct Feb Jun

Oct Feb Jun

Puget Sound Precip

Oct Feb Jun

1900’s

a warmer climatea warmer climate

1.1. StreamsStreams:: Higher flows during

incubation periods; Lower flows,

higher temperatures during

summer/fall rearing and

spawning;

INCREASED STRESSINCREASED STRESS

2.2. estuariesestuaries: : higher temperatures

and migration barriers;

INCREASED STRESSINCREASED STRESS; impacts

on predator/prey fields???

3.3. oceanocean:: warming and

stratification limits nutrients,

warmer temperatures alter

predator/prey fields;

INCREASED STRESSINCREASED STRESS

upwelling winds???

Climate and Salmon habitat

Thermal limits in freshwater habitat

Lost by 2030Lost by 2030Lost by 2060Lost by 2060Lost by 2090Lost by 2090

Figure 16: Future Status of Salmon Habitat (CGCM 2 Model with A2 Emissions)

From Defenders of Wildlife and Natural Resources Defense Council, 2002: Effects of Global Warming on Trout and Salmon in US Streams

Use output from climate model scenarios (summertime air temperature change) to model stream temperature changes, compare with known water temperature limits

Freshwater thermal limits: habitat change by species (DFW/NRDC 2002)

Based on 8 different climate change scenarios (combinations of 3 different models and 4 different emissions scenarios)

upwelling food webs and environmental change in our coastal ocean: the California Current

Cool water, weak stratificationhigh nutrients, a productive “subarctic” food-chain with abundant forage fish and few warm water predators

Warm stratified ocean, fewnutrients, low productivity “subtropical” food web, a lack of forage fish and abundant predators

Progress in Oceanogr., 54 (2002)

Sea surface temperatures and catch-per-unit-effort (cpue) for

steelhead (O. mykiss) on the high seas:

cpue peaks between 6 and 11ºC

(Burgner et al. 1992, INPFC)

High Seas Habitat?

Welch et al’s (1998) Welch et al’s (1998) Thermal Thermal LimitsLimits

1. Salmon are surface oriented

2. They are metabolically constrained by surface ocean temperatures

3. Surface ocean warming will force salmon (sockeye and steelhead) out of the Pacific and into cooler northern oceans as metabolic rates accelerate with warming

Sockeye salmon Sockeye salmon distributiondistribution

(Welch et al (Welch et al 1998)1998)

December

July

20th Century20th Century

distributiondistribution

2xCO22xCO2

distributiondistribution

Temperature tag data from an adult Copper River (Alaska) fall run steelhead, 1998

age 2.3, spawning check at second ocean annulus

Chart provided by Kate Myers, UW FRI High Seas salmon program

High seas, to 40-60m depths Coastal Alaska current

future climate scenarios: different model - emissions combinations give different answers

Tem

per

atu

re C

han

ge (

C)

Emissions uncertainty

model uncertainty

1.5 C1.5 C

6 C6 C

What might climate change look like in the Northwest?

Considering 10 scenarios of future climate, the average changes from baseline:

• 1.7°C (3.1°F) warmer by 2020s

• 2.9°C (5.3°F) warmer by 2050s

• Warming similar in winter and summer

• Wetter winters (almost all models)

• Summer rainfall? – models divided, but all uphold strong seasonality

Millennial Northern Hemisphere (NH) Temperature Reconstruction (blue) and Instrumental Data (red) from

AD 1000-1999

Source: Mann et al. 1999.