// lecture 25 Flashcards
Amount of CO2
Adding different amounts of CO2 makes a very real difference; the amount of warming we’ll produce is directly related to the CO2 we produce. The Atlantic Meridional Overturning Circulation also responds
Atlantic Meridional Overturning Circulation (AMOC)
slows to 25% of present speed, almost nothing, permanently in some business as usual scenarios, but recovers in more modest CO2 scenarios.
Summary: Climate Models
- around 25 models, comparing them offers verification
- composed of equations that describe fluid motions and have parameterizations of small scale processes involving clouds, glacial calving, etc.
- strenuously tested and have been shown to give reliable forecasts of the initial stages of global warming. still many uncertainties.
- differ from weather models because initial conditions are mostly unimportant and instead energy balance is critical. they produce storms for ex, but they are not in sync with reality like weather forecasts are meant to be. only their statistics are relevant.
Is PNW Warming
113 stations with long records; almost every station shows warming and urbanization is not a major source of warming
Temps in the Puget Sound
- a lot of decadal variability in our region: Pacific Decadal Oscillation (PDO) on a scale of around 10 or so years.
- Warm phase of PDO is similar to warm phase of El Nino except there is more amplitude in the extratopics and longer period
Temps in the puget sound
- there’s a lot of decal variabilty in our region
- decadal changes are mostly due to an oscillation in the ocean called the PAcific Decadal Oscillation
- warm phase of PDO is similar to El Nino but more amplitude in extratropics and longer period
predictions for future of PNW
- temps will increase: 1-3 C by 2040 and 1.5-5.5 C by 2080
- precip is uncertain: we’re kind of on the border between drying to the south and moistening to the north; no clear which we will experience of maybe no changes or maybe we will experience both
snowpack
- seasonally melting snow; falls in winter and melts in summer
- important for: water resources in the summer; water temps in summer (salmon) and hydropower
snowpack changes
- with warmer temps, more snow falls as rain and earlier melt
- leads to water stress in sumer when we normally rely on snowmelt for stream flow
- more stream flow with winter rains
- less stream flow in summer because less snow to melt
- warmer stream water in summer bc of lack of snowmelt as well as generally warmer temps
impacts hydropower generation
- winter and spring: increase generation
- summer: decreased generation
- annual: total production will depend on annual precip
impacts on electricity demand
- reductions in winter heating demand
- smaller increases in summer air conditioning demand in the warmest parts of the region
impacts on seattle’s water supply
reduced summertime inflows, increases the size and extending the time of the summertime inflow-demand deficit
is snowpack declng?
- yes in much of western US (some is due to changes in PDO)
- also temps are increasing on days with precip in March and more rain is falling vs snow
- changes in the future will likely be dominated by PDO
- global warming will make a more clear mark eventually
- global warming plus a strong PDO warm phase: worst impacts
impacts on ski industry
- ski conditions at snoqualmie pass could degrade in the relatively near future (2025)
- stevens pass is at a higher elevation and is safer (colder for more snow and less risk for melt, but a greater chance for rain compared to snoqualmie)
Coasts
- rising sea levels will increase the risk of flooding, erosion, and habitat loss along much of WA’s 2500 mi coastline.
- global SLR 8-20” by 2100
