Link between extreme weather and climate change comes into focus

Scientists have typically been cautious when discussing the link between a single extreme weather event and climate change, preferring to focus on broader trends. Previous work, including a paper I wrote with Jay Gulledge four years ago, described a framework for how to think about the link.

But a new report from the National Academies of Sciences (NAS) is making the connection more clear by defining the relative contributions of climate change and other natural sources to the risk of individual weather events. The NAS report – an exhaustive, systematic examination of the peer-reviewed literature – finds high confidence in attribution studies linking individual extreme heat and cold events and climate change, and a more moderate confidence level for several other types of events.

Climate change is making extreme weather more likely. But individual weather events like heat waves or hurricanes are always the product of several risk factors, such as El Nino, climate change or other natural variability, akin to how a poor diet and smoking increase the risk of poor health later in life.

Extreme event attribution attempts to quantify the influence of climate change in comparison to other factors. Determining to what extent climate change strengthened or weakened the event can further our understanding of how much impact climate change is having on our weather.The NAS report assigns a confidence level to the climate impact for a variety of weather events based on three supporting lines of evidence:

  • The physical mechanisms that link climate change to a particular extreme
  • The length and quality of the observational record showing the baseline risk level and changes to date
  • Computational climate modeling showing an increase in risk for a class of extreme event

The report finds the strongest links to climate change for extreme heat and cold, with the highest level of confidence across all three lines of evidence. Drought and extreme rainfall have medium confidence for physical understanding, observation and modeling. Extreme snowfall has medium conference for two out of three, physical understanding and modeling, while the observational record for snowfall is poor.

This winter was cold for some, not for all

A lot of folks in the eastern half of the United States are breathing a sigh of relief that spring is just around the corner. Average temperatures this winter were among the Top 10 coldest in some parts of the Upper Midwest and South. More than 90 percent of the surface of the Great Lakes is frozen, the highest in 35 years.

But while East Coast and Midwest kids have been sledding and their parents have been shoveling, it has not been cold everywhere. In fact, many areas are unusually warm.

In Alaska, January temperatures were as high as they have been in 30 years. The Iditarod dogsled race was especially treacherous this month because of a lack of snow. Crews had to stockpile and dump snow on the ground at the finish line in Nome, where temperatures earlier this winter broke a record.

Globally, January was the fourth warmest on record – really – despite pockets of well-below-normal temperatures in parts of the United States. According to the National Oceanic and Atmospheric Administration (NOAA), most areas of the world experienced warmer-than-average monthly temperatures. For example:

  • China experienced its second warmest January on record.
  • France tied its warmest January.
  • Parts of Brazil and Australia saw record heat.
January temperatures were above normal for much of the globe.
January temperatures were above normal for much of the globe.

Why we shouldn’t throw out flood insurance reform

It’s not surprising that homeowners in flood-prone areas are asking their representatives in Congress to protect them from higher flood insurance bills.

Here’s the question. Who is going to protect them from higher floods?

Congress in 2012 did the right thing in fixing a broken flood insurance system that has fallen $24 billion in debt, largely because the price of flood insurance hasn’t for many years matched the risk of a flood. Now, both the House and Senate have passed bills that would undo many of these reforms.

Congress should find a way to address both the immediate and long-term concerns of their constituents, and the rest of the nation. We can’t ignore the plight of families facing hefty insurance increases, and we must ensure that the process of making flood insurance reflect flood risk is fair and transparent. But we also can’t ignore the increasing costs and risks associated with growing coastal development in an era of rising seas and heavier precipitation.

Among the problems with the National Flood Insurance Program (NFIP) that we outlined in a C2ES brief:

Research affirms climate impacts are already here

This year saw the release of three notable reports related to climate science. Together, they paint a clear picture:

  • Global warming is largely caused by human actions,
  • The future climate is likely to be very different without significant cuts in greenhouse gas emissions,
  • Climate change impacts are already occurring, and
  • Some future impacts could be catastrophic to communities, businesses and ecosystems.

The draft National Climate Assessment (NCA) was released for public comment in January, and the major conclusions aren’t expected to change when the final report is released in 2014. U.S. average temperature has increased by about 1.5°F since 1895 with 80 percent of this increase occurring since 1980. The report projects that temperatures will continue to rise, with a 2° to 4°F increase occurring in most areas over the next few decades. According to the report, these changes are contributing to an increased risk of extreme weather, coastal flooding, loss of biodiversity, and negative impacts on public health.

Sandy Anniversary is a Reminder of the Need for Better Protections

A year after Hurricane Sandy, more work remains to be done to help families and communities fully recover. But another pressing need, not only for those who were in Sandy’s wake but for all of us, is to learn from the storm’s devastating impacts and reduce the risk of future damage and loss of life.

Hurricane Sandy's estimated $65 billion in damages make it the second costliest hurricane in U.S. history, surpassed only by Hurricane Katrina.

Building resilience to the impacts of major coastal storms like Sandy—and to other types of extreme weather that are becoming more intense and frequent as a result of climate change—will require a commitment to better protect infrastructure and implement  policies to help get people out of harm’s way. Both efforts should take into account how future sea level rise can amplify storm surges, potentially making future impacts greater than what we’ve experienced in the past.