Science

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.

Ten Myths About Intellectual Property Rights and the Montreal Protocol

Ten Myths About Intellectual Property Rights and the Montreal Protocol

April 2016
 

By Steve Seidel and Jason Ye

Download the Brief (PDF)

This brief explores myths and facts about intellectual property rights as they are covered in the Montreal Protocol, an agreement to limit high global warming potential (GWP) gases. 

Jason Ye
Stephen Seidel
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Action on HFCs heats up

We’re seeing new movement toward phasing down the fastest-growing group of greenhouse gases – hydrofluorocarbons, or HFCs. These chemicals are widely used in refrigerators, air conditioners, foam products, and aerosols. And while they don’t stay in the atmosphere long, they can trap 1,000 times or more heat compared to carbon dioxide.

This week, the U.S. Environmental Protection Agency (EPA) proposed new regulations demonstrating its commitment to limiting the use of HFCs domestically. It proposed changes to its significant new alternatives program (SNAP) aimed at expanding the list of acceptable alternatives that minimize impacts on global warming while also restricting the use of HFCs in sectors where alternatives are now available. EPA estimates the proposed rule could avoid up to 11 million metric tons of carbon dioxide equivalent in 2030, which is equal to the energy-related emissions from about one million homes for one year.

Internationally, one sign of growing support for acting on HFCs came this month during the first visit by a U.S. president to Argentina in almost two decades. President Obama and newly elected Argentinian President Mauricio Macri explored opportunities to partner to address global challenges like climate change.

They affirmed their commitment to take action this year to amend the Montreal Protocol to phase down HFCs, which are substitutes for ozone-depleting chlorofluorocarbons (CFCs) that were successfully phased out under the 1989 Montreal Protocol. The two leaders also endorsed the understandings reached at the Dubai Montreal Protocol meeting in November 2015 on financial support for developing countries to implement an HFC phasedown.

A key opportunity will come next week when Montreal Protocol negotiators meet in Geneva to build on the progress made toward reaching agreement this year on an HFC phasedown amendment.

Collaboration for Climate Resilience in Stamford, Connecticut

Collaboration for Climate Resilience
in Stamford, Connecticut
 
March 2016
 

The city of Stamford, Connecticut, is a corporate hub with more than 125,000 residents, the third largest city in the state. As a coastal city, Stamford is vulnerable to threats of climate change, extreme weather, and natural disasters, making it imperative for the city’s leadership to plan for resilience.

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Climate Change Impacts in Anchorage

Climate Change Impacts in Anchorage

March 2016

Download the Fact Sheet (PDF)

Climate changes will impact the entire Anchorage community. Businesses of all sizes are an important part of the community, and will experience many different risks, such as disruptions to their supply chain, financial losses from extreme events, and threats to the health and safety of their employees. The business community in Anchorage can work together with city and state agencies, along with other stakeholders to evaluate potential risks and take steps toward enhancing the community’s resilience. 

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Approaches to Structuring a High Ambient Temperature Exemption

Approaches to Structuring a High Ambient Temperature Exemption 

March 2016

By Steve Seidel, Jennifer Huang, and Stephen O. Andersen

Download the Brief (PDF)

As parties to the Montreal Protocol consider an amendment to phase down hydrofluorocarbons (HFCs), one critical concern is whether suitable alternatives for air-conditioning applications are available and adequately demonstrated for cooling capacity and energy efficiency under conditions of high ambient temperatures. Given the critical importance of these applications, one option being considered by parties is to provide a time-limited exemption for those uses in countries that could be adversely impacted by high ambient temperatures. This paper looks at a number of options for how such an exemption might be structured.

Jennifer Huang
Stephen O. Andersen
Stephen Seidel
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2015 was the warmest year on record

Image courtesy NOAA

This visualization from NOAA shows much warmer than average or record warm temperatures across much of the globe in 2015, the warmest year on record.

The data are in, and 2015 was officially the warmest year globally ever recorded. We’ve been keeping temperature records since 1880. The last time the record was broken? 2014.

What’s interesting is just how much warmer 2015 was. The observed annual average surface temperature was more than 1.8° F (1° C) above the 19th century average, according to the National Oceanic and Atmospheric Administration (NOAA) and the National Aeronautics and Space Administration (NASA). That’s already half the warming countries have agreed to as the international limit.

And 2015 was about a quarter of a degree Fahrenheit warmer than 2014. That might seem small, but it’s actually huge when compared to the year-to-year differences observed in the record.

A strong El Niño, when the surface ocean in the Eastern Pacific basin warms, contributed to the record warmth of 2015. But even compared to other El Niño years, 2015 set records. The agencies reporting the data attribute this to the long-term warming trend due to the increase of greenhouse gases in the atmosphere.

As with all climate and weather data, the 2015 data shows some variability. Not all locations set high temperature records, and parts of the North Atlantic Ocean actually set a cold temperature record.

In the contiguous United States, 2015 was the second warmest year on record, with 2012 still holding the top spot. It was the 19th consecutive year that the annual average U.S. temperature was more than the 20th century average.

Attributing extreme weather events to climate change

It is well known that climate change will alter the occurrence of extreme weather events like heat waves, droughts, and severe storms. But weather is unpredictable and naturally variable, so how can we be sure climate change is happening today?

Climate change attribution

Scientists have recently developed tools for so-called event attribution, to say (through the use of statistics) whether a particular extreme weather event is caused by climate change. The fourth annual report on event attribution was just published in the journal Bulletin of the American Meteorological Society (BAMS). Researchers around the globe used different methods to assess 28 events that occurred in 2014. They found that some of these events probably would not have happened without climate change.

Why ‘probably’?

Any individual weather event is a part of a chaotic and complex system (yes, those are the technical terms). Because of this, it is theoretically impossible to predict weather over any meaningful timescale. So scientists turn to probabilities.

When your local weather forecaster tells you there’s a 30 percent chance of rain, that number doesn’t come out of a hat. The percentage comes from many weather models run over and over again. A 30 percent chance of rain tomorrow means that for every 100 model simulations of the weather tomorrow, 30 had rain.

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Significant progress toward limiting HFCs under the Montreal Protocol

In an important breakthrough, parties to the Montreal Protocol meeting in Dubai have agreed to a path forward aimed at phasing down hydrofluorocarbons (HFCs), a class of highly potent greenhouse gases. This progress adds to the momentum leading up to the UN climate talks starting later this month in Paris.

HFCs, chemicals widely used in refrigeration, air conditioning, and foam blowing, were developed in response to limits on ozone-depleting substances under the Montreal Protocol.

The United States and 40 other countries had put forth a range of proposals this year for phasing down HFCs. While these efforts fell short of producing a consensus amendment, extensive discussions throughout the week resulted in a path toward delivering an HFC phasedown amendment at a special, additional meeting of the parties to be held in 2016.

Are 2015's extreme weather events driven by climate change or El Niño?

Hurricane Patricia (Photo: NASA Earth Observatory)

Record warmth, increased precipitation, and more intense tropical cyclones.

These are just a few of the consistent predictions from models investigating our future in a world with climate change. Or, it’s a list of some of the impacts of the periodic weather pattern called El Niño.

So which one has been driving some of this year’s extreme weather events?

A record year for Pacific tropical cyclones

The National Hurricane Center reports that eight major hurricanes (Category 3 or higher) have developed in the eastern North Pacific Ocean so far this season. This is consistent with the characteristics of El Niño that have been shaping up over the course of the year.

During an El Niño year, the surface ocean in the Eastern Pacific basin warms (it’s usually very cold) and the trade winds in the area weaken. These two meteorological developments favor the formation of tropical cyclones, the general term that includes hurricanes and related systems. Hurricane Patricia achieved record strength in a record short period of time this month, becoming the strongest Pacific hurricane to make landfall. Meanwhile, climate change will probably not change the number of hurricanes overall, but warmer ocean surface temperatures and higher sea levels are expected to intensify their impacts.

Driver: El Niño

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