Action 119. Find out what the National Climate Assessment means for us in the Northwest

Hotter summers, more extreme precipitation events, increased sea level rise anywhere from a few inches to multiple feet, increased forest loss and reduced carbon storage capacity, lower snowpack, increased stress on some of our agricultural systems, and folks, the Yakima Valley is predicted to get royally screwed under climate change.  These are the headlines I took away from the excellent webinar presentation about the findings of the National Climate Assessment (NCA) and their relevance to the Pacific Northwest hosted by the Union of Concerned Scientists (UCS). UCS is hosting a series of these webinars throughout May to talk about the results of the NCA on a region-by-region basis.

The NCA is a comprehensive report that informs us about how climate change is effecting and is expected to affect the US into the future under a variety of emissions scenarios guided by IPCC modeling. The NCA is a creation of the U.S. Global Change Research Program, which was established by Presidential Initiative in 1989 and mandated by Congress in the Global Change Research Act of 1990 to “assist the Nation and the world to understand, assess, predict, and respond to human-induced and natural processes of global change.” The latest version of the NCA that was just released this spring is the third iteration of this report, with each new version benefitting from a larger set of information and data about the linkages between greenhouse gases and climate change impacts. I highly recommend checking out the NCA website– it is extremely well presented, with a great balance between articulately communicating major messages, while allowing readers to dive deeper into details if they choose.

The Northwest’s regional webinar was hosted by some of the report’s primary authors, including Dr. Amy Snover, Director of the Climate Change Impacts Group at the University of Washington, Dr. Philip Mote of OSU, and Dr. Steve Running of the University of Montana. The speakers did an excellent job articulating the major points of the NCA as it relates to our region. Here’s some more detail on the major topics covered in the webinar, and you can read all about these in the Northwest Region Chapter of the NCA:

It’s getting hot in here: the report explores a variety of potential impacts under a range of emissions scenarios.There is plenty of uncertainty as to what path the world will take with respect to our greenhouse gas emissions, but one thing is for sure: based on the GHGs we have already emitted, global temperatures are going to continue to rise. That rise could be anywhere between a few degrees, and several, depending on what path we chart. An increase in average annual temperature of 3.3°F to 9.7°F is projected by 2070 to 2099, with the largest increases occurring in summer. Most definitely, these temperatures will be highly variable and regionalized, depending on many factors, and particularly for our area ocean circulation patterns will play a large role in where and to what extent warming is felt in the Pacific Northwest.

Rain, rain, not going away: The Northwest is exceedingly lucky under most climate change scenarios in terms of total precipitation. Unlike other areas of the US, notably central California and the Southwest, we are not predicted to undergo marked declines in rainfall in most parts of our region. That being said, we will still face hydrologic challenges. Extreme precipitation events, such as severe storms and flooding, are likely to be more common in our future. Recognizing and preparing for these extreme events is going to become extremely important in our ability to mitigate increasing flood risks.

Low Snow is a big Oh No: Changes in snowpack are a serious issue facing the Pacific Northwest. Since around 1950, area-averaged snowpack on April 1 in the Cascade Mountains has decreased about 20%, spring snowmelt occurred 0 to 30 days earlier depending on location, and summer flow decreased 0% to 15% as a fraction of annual flow. By 2050, snowmelt is predicted to start 3 to 4 weeks earlier than the current average timing. We can expect these trends to continue, and likely accelerate. These changes are extraordinarily meaningful for the ecosystems that have developed over thousands of years in response to the seasonal rhythms of snow-driven river systems. And for a region which produces 40% of the entire country’s hydropower, changes in the timing and volume of snowmelt have extraordinarily important repercussions for energy production.

River systems that are currently based primarily or largely on rainfall will see more variability in peak and low water events, but it is the interior basin rivers that are going to feel some of the greatest impacts of climate change. Take a look at the predicted reductions in summer flows in Washington State (figure on the right below) and shifts in the timing and volume of runoff in the Yakima River Basin (figure on the left) under an IPCC modeling scenario which predicts emission increases under robust economic growth followed by gradual emissions reductions over time. Note particularly the major shifts predicted in the timing of stream flows to the Yakima River Basin in the figure on the left: these changes have enormous repercussions for agricultural water availability, timing, and use of the basin by fish and wildlife depending on these flows.

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Caption: Areas of Seattle projected by Seattle Public Utilities to be below sea level during high tide (Mean Higher High Water) and therefore at risk of flooding or inundation are shaded in blue under three levels of sea level rise, assuming no adaptation. (High [50 inches] and medium [13 inches] levels are within the range projected for the Northwest by 2100; the highest level [88 inches] includes the compounding effect of storm surge, derived from the highest observed historical tide in Seattle. Source: National Climate Assessment

 A rising tide: Sea Level Rise is a very tricky issue to understand, particularly at sub-regional levels. Globally, sea level is predicted to rise somewhere between 1 and 4 feet by 2100. A three foot range may not seem like a big difference, but when you consider that 140,000 acres of coastal areas of the Pacific Northwest lie within 3.3 feet of the high tide line (and nationwide, about 3.5 million people live within a few feet of high tide), where that number actually falls makes a huge difference to the nature and extent of the threat to coastal habitats and infrastructure. Actual sea level rise depends on a huge number of variables, including the rate of emissions increases and/or reductions over time; the rate of melt of major ice sheets; and local tectonics- should our area experience a major earth quake in the Cascadian Subduction Zone, this could reverse centuries of tectonic uplift and increase relative sea level upwards of three feet for many areas, while causing uplift relative to sea level in others.

Not-So-Hard Hard Times for CalcifiersOcean acidification is an extraordinarily concerning issue for our global oceanic food chain. Much of the plankton that forms the foundation of our oceanic food web is calcified, and in order to create their shells, these organisms need a relatively basic ocean chemistry. As our waters move towards more acidic conditions, ocean chemistry makes it more difficult for calcified organisms to create and maintain their shells. In the Pacific Northwest, we already deal with variable and sometimes stressful conditions for our calcifiers, including natural patterns of upwelling of deep ocean waters that are lower in pH. Adding additional acidity to conditions that can already be marginal for calcifiers is likely not good news for the 30% of our marine species in Puget Sound that are calcifying organisms, as well as for the broader oceanic food chain that depends on calcifying organisms.

 

Can’t see the forest for the lack of trees: US Forests and wood products absorb about 16% of the carbon dioxide emitted by fossil fuels in the US each year. Our country’s forests are an important carbon sink, but they are not necessarily predicted to remain that way. Extreme temperatures, water reduction, increasing frequency of forest fires, and increasing forest insect and pathogens are a deadly combination for our dry western interior forests in particular. Dr. Running noted that we are approaching a point where there is no “fire season”, but that wildfire is becoming something we need to think about as a year round risk. Mountain pine beetles pose a serious threat contributing to forest mortality and wildfire risk, and  the elevation of suitable beetle habitat is projected to increase as temperature increases, exposing higher-elevation forests to the pine beetle, in the first half of this century, but ultimately limiting available area as temperatures exceed the beetles’ optimal temperatures. Climate change scenarios predict that towards the end of this century, many if not most of our subalpine and alpine forests will completely convert to other vegetative community; an astonishing rate of conversion for ecosystems that have been relatively stable for thousands of years.

One of the issues Dr. Running presented that was particularly interesting was whether we need as a nation to seriously rethink our forest policies to remove dead fuels (diseased and downed wood) from forests to reduce forest fire risk and also provide a source of materials for biofuel and other purposes. If this makes anyone nervous and reminds them of Bush’s failed log salvage policies of the mid 2000s- well, it should, but it also might be something that we have to put on the table as we consider how to reduce our forest fuel as climate change heats up our risk of catastrophic fires.

Under the likely range of climate change scenarios, then, the Pacific Northwest is exceedingly fortunate in a few regards: our reductions in rainfall are not expected to be as severe as other regions, and our diversity of ecosystems and topography affords us a reserve of variability that will likely help buffer some of these changes. However, we will not escape many of the coming changes to our oceans, land and waters. But knowing hydrologic and other major changes are coming is an opportunity to prepare and adapt to these changes. We would be foolish to miss the narrowing window of opportunity to stay ahead of some of these predicted changes where we can; and some cities including Seattle and Olympia are taking some steps in the right direction of assessing municipal vulnerability to climate change.

Despite the uncertainties, one thing the NCA makes crystal clear is that we are experiencing and will experience dramatic and rapid changes in our climatic and ecological systems in the decades to come, and that the severity of those changes depend directly on the choices we make as a nation and a world about our ongoing greenhouse gas emissions.

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