Monthly Archives: September 2016

We just had five 1,000-year floods in less than a year. What’s going on?

By / Bio / Published: September 6, 2016

A 1,000-year flood is supposed to be extremely rare. Its chance of occurring in a given year: 0.1 percent.

So how do we explain that in the span of just five months, the United States logged no fewer than four deadly 1,000-year floods in states as widespread as Texas, West Virginia, Maryland and Louisiana – following a 1,000-year-flood that ravaged South Carolina last October.

It appears that the calculation of a 1,000-year event may no longer be the most accurate statistic. It was based, as are our increasingly common 100-year natural disaster events, on data from the past. We may, in other words, already have shifted so far into a new climate regime that probabilities have been turned on their head.

Climate change “supercharges” normal weather

Like any climate scientist will tell you, there is more to the story than what you see on the surface.

All climate and weather events are influenced to some degree by both natural climate variations and human-made climate change. The amount that each of these influences can exert on a particular event can theoretically range from 0 to 100 percent.

Rigorous scientific analysis has found that the extreme rainfall that caused a Texas flooding in May of 2015, for example, was caused by a fairly typical rainfall pattern associated with that year’s El Niño, a naturally occurring climate cycle, which had been supercharged by human-made climate change.

Working in tandem, these two phenomena together produced one of the largest multi-day flooding events Texas has ever experienced.

Recent floods continue the trend

But what about more recent floods like the one in Baton Rouge or Ellicott City, Maryland?

Attributing short-term extreme weather events to climate change is not a trivial exercise, even as the science of climate attribution has advanced rapidly over the last decade.

Using high-powered models and complex statistical analysisof observations, credible scientific statements can now be made about how climate change affect the frequency or intensity of a specific weather event.

There is an inevitable time delay between the occurrence of an event and the complete dissection of its various causes. This is why we cannot yet say with certainty that last month’s flooding in Baton Rouge, or the flash flood that devastated Ellicott City in July, were due to climate change.

71% more heavy rain since the 1950s

If you’re anything like me you don’t enjoy waiting for answers. So while it’s certainly wise to await the scientific analysis that is sure to be coming down the pike, we can still think about these events in the climate change context.

We know that as the global average temperature rises, more water evaporates from the oceans. This, in turn, increases the amount of atmospheric moisture that is available for storms to process into rainfall.

Increases in heavy downpours by region 1958-2012. Source: NCA

In fact, observations over the last 60 years indicate that over the United States, the amount of water falling in heavy rain events has increased substantially, and an astonishing 71 percent over portions of the mid-Atlantic and northeastern U.S.

In other words, if there were two storms with an identical structure over Boston, Massachusetts – one in 1955 and one in 2016 – the one in 2016 would, on average, produce 71 percent more rainfall.

Bottom line is that the heavy rainfall and disastrous flooding events that we continue to experience are certainly consistent with what the science tells us about the impacts from increasing global temperatures.

These floods are another reminder that we must change that trajectory.

Photo source: Flickr

Posted in Greenhouse Gas Emissions / Comments are closed

In Win for Environment, Court Recognizes Social Cost of Carbon

By / Bio / Published: September 1, 2016

This post was co-authored with Martha Roberts. It originally appeared on EDF’s Market Forces)

If someone was tallying up all the benefits of energy efficiency programs, you’d want them to include reducing climate pollution, right? That’s just common sense.

Thankfully, that’s what our government does when it designs energy efficiency programs—as well as other policies that impact greenhouse gas emissions. And just this month, this approach got an important seal of approval: For the first time, a federal court upheld using the social cost of carbon to inform vital protections against the harmful impacts of climate change.

So what is the social cost of carbon and why does it matter? It’s a crucial part of the development of climate safeguards and essential to our understanding of the full costs of climate pollution. We know that climate change is a clear and present danger now and for future generations—one that will result in enormous costs to our economy, human health and the environment. And yet, these “social” costs are not accounted for in our markets, and therefore in decision making. It is a classic Economics 101 market failure. Every ton of carbon dioxide pollution that is emitted when we burn fossil fuels to light our homes or drive our cars has a cost associated with it, a hidden one that is additional to what we pay on our utility bills or at the gas pump. These costs affect us all – and future generations – and are a result of the negative impacts of climate change. If we don’t recognize these hidden costs—we aren’t properly protecting ourselves against the dangers of climate pollution.

The social cost of carbon (or SCC) is an estimate of the total economic harm associated with emitting one additional ton of carbon dioxide pollution into the atmosphere. To reach the current estimate, several federal agencies came together to determine the range and central price point – roughly $40 per ton – through a transparent and rigorous interagency process that was based on the latest peer-reviewed science and economics available, and which allowed for repeated public comments.

It’s critical that we protect against the damages and costs caused by climate pollution. So it’s a no-brainer that when considering the costs and benefits of climate safeguards, we must take into account all benefits and costs – and that means including the social cost of carbon.

In their court opinion, the Federal Court of Appeals for the Seventh Circuit agreed wholeheartedly. Harvard Law Professor Cass Sunstein noted that their decision “upholds a foundation” of “countless” climate protections. In particular, their opinion made two important findings:

  • First, the court affirmed that the DOE was correct to include a value for the social cost of carbon in its analysis. The judges concluded that “[w]e have no doubt” that Congress intended for DOE to have authority to consider the social cost of carbon. Importantly, this conclusion reinforces the appropriateness of including the SCC in future carbon-related rule-makings.
  • Second, the court upheld key choices about how the SCC estimate was calculated. The court agreed that DOE properly considered all impacts of climate change, even those years from now, or outside our borders. These choices, the court concluded, were reasonable and appropriate given the nature of the climate crisis we face.

DOE itself acknowledged “limitations in the SCC estimates.” We couldn’t agree more. As new and better information about the impacts of climate change becomes available and as our ability to translate this science into economic impacts improves, regulators must update the current social cost of carbon estimate. There is still much we do not know about the full magnitude of climate impacts and much that cannot be quantified (as is true of all economic impact analysis) – which means that SCC estimates are likely far lower than the true impact of climate change. But as the Seventh Circuit recognized, their inclusion is a vital step in the right direction for sensible policy-making.

This decision already has positive implications more broadly—in particular, for the Clean Power Plan, our nation’s historic program to reduce carbon pollution from power plants. Just last week, EPA submitted a letter in the Clean Power Plan litigation noting that the Seventh Circuit’s decision further demonstrates the error of challenges to the treatment of costs and benefits in the Clean Power Plan rulemaking. It’s just another affirmation of the rock-solid legal and technical foundation for the Clean Power Plan.

Posted in Clean Power Plan, Economics, Policy / Comments are closed