Global Warming: The Basics and Implications for the Northwest Cliff Mass, University of Washington

There is a great deal of contradictory information about global warming

A variety of local environment groups have proposed that global warming has caused our weather to become more extreme

In contrast, others hold that the lack of warming of the planet during the past ten years indicates that global warming is no real threat George Will

..and that scientific consensus is a myth

Some ask: How can scientists predict climate when they can’t get the next week’s weather forecast right?

…but thousands of scientists from around the world have written a series of reports indicating the imminent threat of global warming due to mankind’s influence

IPCC Reports

What is the truth? What is biased and wrong? What do we know for sure? What are the uncertainties? What will happen here?

The Problem: greenhouse gases are increasing

Greenhouse Gases Act as Atmospheric “Blankets” and Warm the Earth Carbon Dioxide Water Vapor Methane Nitrous Oxide … and others

We understand the greenhouse effect Graphic courtesy of the National Park Service

We Can Predict the Future Effects of More Greenhouse Gases Using “Climate Models” Sophisticated computer simulations based on the physics of the atmosphere. Nearly identical to weather prediction models, which are tested every day. These models are very good, but not perfect.

A Major Question Is How Greenhouse Gas Emissions Will Change in Time

Substantial Uncertainties of the Magnitude of the Forcing Exist

Warming Is Clear But Substantial Uncertainties Exist

Climate Model Output for 2100: Global Warming Will Not Be Uniform

Global Models Do Not Have the Resolution to Describe the Local Implications of Global Warming—Regional Downscaling is Needed

Bottom Line It is clear that the earth as a whole will warm and that the rate of warming will increase later in the century. There is substantial uncertainty in the magnitude of the global warming during this century (roughly 1-4°C globally). Even more uncertainty exists regarding the local implications of global climate change, both natural and man-induced.

Global Warming Implications in the Northwest It appears that there has been very little warming here during the past 30 years. This makes a lot of sense--our weather is controlled by the Pacific and the eastern Pacific is one of the last places that will warm significantly. Although global warming will be weaker and delayed here…it will happen in force by the end of the century.

Cascade snowpack hasn’t changed in the last 30 years

Change in Winter Surface Air Temperature (°C) for Air Temperature Trend ( )

Can We Predict Climate When We Can’t Forecast Next Week’s Weather?

In weather prediction we forecast the exact state of the atmosphere at some time in the future Tomorrow’s high in Spokane will be 67F It will rain tomorrow afternoon after 3 PM

In Climate Prediction we DON’T do this. We predict average quantities over extended periods. Example: the mean winter temperatures will be 3F higher over the Pacific Northwest. MUCH easier to do. Furthermore, the average conditions are closely controlled by the amount of radiation reaching and leaving the planet--and we can figure that out fairly well.

Should we expect stronger storms and more floods under global warming?

We don’t know. And there is no certainty that stronger storms will occur here. The number of windstorms and floods have increased during the past decade or so in Washington, but DECREASED in Oregon. Storms follow the jet stream --a current of strong winds in the upper atmosphere--and most climate models predict the jet stream will weaken and move northward. Thus, it is possible that storms here might WEAKEN or move away from us under global warming.

Finally, does the lack of warming during the last ten years mean anything?

No, one should expect such level periods Atmospheric temperature trends are a combination of man-caused global warming and natural variations, which are quite significant. The global warming signal will increase rapidly this century, but natural variations will not. So one expects some short periods when natural cooling balances out global warming. Eventually, man-induced global warming wins.

Regional Simulations of the Local Impacts of Global Warming

Change in Winter Surface Air Temperatures (F)

-40% 0%+40% Change in Snowpack from 1990 to 2090

Advice: Don’t buy this after 2050!

Bottom Line The earth will warm substantially during this century, but there are considerable uncertainties. Global warming will be delayed here, but substantial changes will occur by the end of the century

The End

PDO