Climate Change Blogs

Wagging the Dog

Published: December 24, 2014
Wagging the Dog

My piece that was published last week at The Conversation entitled, What would happen to the climate if we stopped emitting greenhouse gases today? has had more than 350K reads – most read science and technology article of the week. Last week in my WU blog, I provided some background material trying to make that piece a little more intuitive. In this blog, I will expand on a couple of ideas that came up in the conversation.

Ocean, Atmosphere and History: It is interesting to me how the paths we take frame our perceptions and establish our social structure and norms. What an arcane statement.

Meteorology and oceanography have been studied as parts of natural science for centuries. Paul Edward’s book A Vast Machine gives an excellent historical perspective. As population grew, as agriculture expanded, and as exploration, colonization and commerce became global, meteorology and oceanography took on more and more important roles in society. The studies moved out of the curiosity realm of a handful of natural scientists.

For a variety of reasons, meteorology evolved quickly in the early twentieth century. Perhaps the most compelling reason for the emergence of meteorology was the impact on people and society. When we think about impacts, we are first drawn to risks from extreme weather such as tornadoes, hurricanes and blizzards. However, there is a more, perhaps, benign aspect, where weather that is not extreme is used in planning. When to fly? When to plant? When to bet against Peyton Manning? Weather is important and it is consequential to people on a day-to-day basis.

The need for weather information in both peace and war brought motivated people to problems of forecasting. This led to the development of ways to measure the atmosphere. With the recognition that the atmosphere behaved as a fluid, there was development of the foundational theory of dynamical meteorology. Physical meteorology emerged as thermodynamics was applied to understand precipitation. As the observational and theory-based knowledge were conflated, it was realized that there was the potential to predict the weather. The emergence of digital computers greatly advanced predictive skill and the development of atmospheric models.

For many years, weather forecasting models did not even calculate the heating from the Sun and the cooling of the Earth to space. Their goal was to take an observed snapshot of the weather and to project that snapshot forward in time as long as possible. When started, practitioners of numerical weather prediction were excited when a day or two of skill was realized. The ocean? The ocean was largely absent in early models. Some years later it was recognized that sea surface temperatures might influence weather forecasts.

We have, here, the fact that predictive models developed from not only an atmosphere-centric point of view, but from a weather point of view. The development was framed by the limitations of computational and financial resources as well as by the expert judgment of what the scientists at the time thought was the most important thing to do next. The history and culture of weather forecasting had and have an enormous impact on climate science.

While weather-forecast science evolved with a compelling, societal purpose, physical oceanography and climatology remained more in the realm of the curiosity-driven. Though, no doubt, advocated and recognized as intellectually and societally important, these disciplines did not have the societal imperative. For example, though important to shipping, surface currents in the ocean are relatively slow changing relative to how long it takes a ship to move rubber ducks from Hong Kong to the U.S. Adequate knowledge of surface currents might, arguably, be obtained from mean measurements. As for climate science, original climate models were viewed more or less as a weather model, except that solar radiation was more important than weather.

Trying to explain the relation between the heat in the ocean and air temperature in What would happen to the climate if we stopped emitting greenhouse gases today? and my WU blog brought home to me the deficiencies of the atmospheric point of view. I have written about Point of View before and, specifically, that we are most interested in how climate affects us; therefore, we are most interested in the surface air temperature. Years ago, I understood that if I were to take a balanced look at climate science, then the role of the ocean was under appreciated, under observed, under represented and under communicated. (Same true for ice sheets.)

The discussion about the atmosphere and ocean put me in mind of the arguments about whether or not the Sun revolved around the Earth (geocentric) or the Earth revolved around the Sun (heliocentric). The intuition that the Sun revolved about the Earth follows from our point of view and that our point of view is in some way fundamental. Observing the motion of the Sun and the planets in the sky, it was possible to argue that the Sun revolved around the Earth, explaining planetary motion with occasional epicycles, circles within circles that explained why the planets moved backwards. Eventually this perspective collapsed under the scrutiny of observations and physics.

If we followed the energy, then the natural focus of climate science would be the oceans. In fact, when I first heard about global warming (in the 1960s), many scientists said global warming would not be a problem for humans because the oceans would harmlessly absorb the excess heat. The ocean was viewed as a big static heat sink – big carbon dioxide sink as well. But the ocean moves energy and carbon dioxide around. What goes in can come out. If the focus in climate science and climate-change communication was on the ocean, then the temperature variability of the atmosphere would be largely framed as a response to the ocean. Our current perspective, the one that I took in the Conversation piece, is a bit like the tail wagging the dog. It is not incorrect; however, it frames climate change in a way that renders some very fundamental aspects of climate change difficult to communicate.

Figure 1: The tail wagging the dog from sketchedout wordpress blog.
Categories:Climate Change

Turn Off the Carbon Dioxide Emissions – It Still Gets Warmer

Published: December 12, 2014
Turn Off the Carbon Dioxide Emissions – It Still Gets Warmer

I have a piece that went up today on a new-to-me website called The Conversation. It’s title is: What would happen to the climate if we stopped emitting greenhouse gases today? I try to explain with not so many words - if we stopped emitting carbon dioxide today, why does the temperature keep going up.

In this blog, I will provide some background material that might make things more intuitive for the weather-savvy crowd – or even the wine-growers amongst us. A couple of my previous blogs that I will call upon:

Still Following the Heat
Point of View

If you compare the climate and weather of, say, Kansas and coastal California, there are some distinct differences. Kansas has higher swings of temperature from summer to winter. In the summer, Kansas is often very hot and in winter it can be brutally cold. Along the California coast, such extremes are not as common. In fact, one doesn’t have to go all the way from the Pacific Coast to Kansas to find such extremes of variability. You only have to go, east, over the relatively small Coast Range of mountains in California to find larger swings of temperature. This is especially true in summer, when driving, east, from San Francisco, through Oakland, to Livermore you can go from quite chilly in San Francisco to over 100 degrees F in Livermore. That’s about 50 miles. (Does any one know what ever happened to Roderick’s BBQ? Prefer, local on-ground verification.)

One reason that the temperature variability on the coast is smaller is because of water. In our California example, the Pacific Ocean and San Francisco Bay are quite cold, and they are large enough to influence the temperature over the land for a few miles. By the time you get to Livermore, this moderating effect of the cool water is diminishing. Many of us have the intuitive feeling that large bodies of water moderate the temperature variability that we feel. That’s one of the reasons we like to go to the seashore or lake shore during the summer. Weather and climate scientists call this a marine, maritime or oceanic climate – from the American Meteorological Society (AMS) Meteorology Glossary “A regional climate under the predominant influence of the sea, characterized by relatively small seasonal variations and high atmospheric moisture content; the antithesis of a continental climate.” Another type of climate largely defined by oceanic moderation / modification is the Mediterranean climate, “Characterized by mild, wet winters and warm to hot, dry summers; typically occurs on the west side of continents between about 30° and 45° latitude.”

This moderating effect of water is reasonably well known. It doesn’t require a whole ocean. The same effect is seen in Great Lakes of the United States, which is, really, a coupled lake-land-atmosphere climate. And, of course, on even a smaller scale, people of Michigan have a huge summer lake culture, where to escape the oppressive 85 degree F days of August, they go to the less-than-great lakes that are throughout the state. (Keeping with a recent dubious theme Kid Rock. This pretty much explains at least one of my students.)

Getting to science, we understand that air and land heat up and cool down faster than bodies of water. There are a number of reasons for this. Both water and air are fluids, so when they get heated, there is the possibility of motion, which, ultimately, mixes hot and cold parts of the fluid. It takes, however, more heat to change the temperature of a mass of water than it takes to change the temperature of an equal mass of air. Or, for the same amount of heat, the air warms up faster than the water. Scientists talk about specific heat and heat capacity, and there are definitions, again, in the AMS Glossary, but I prefer specific heat is “the number of calories required to raise the temperature of 1 gram of a substance 1°C, or the number of BTU's per pound per degree F.” Generically, the amount of energy required to raise the temperature of a certain amount of mass of a substance a certain number of degrees. The specific heat of water is about 4 times that of air.

From a different perspective, if you take away the heat, the water takes longer to cool down.

Let’s stick with the more intuitive and experiential approach. I spent a lot of youthful time at the mouth of the Neuse River in North Carolina. Here we scooped soft shells, gigged flounder, developed our relationships with eastern diamond backs and stood in the water and felt the shock of distant lightning. (These are Southern things.) Later in life I spent 30 years on the shore of the Chesapeake Bay. One of the things you notice in these places is the slight shift of the seasons. The daffodils were a full two weeks later on the Bay than up in Greenbelt, MD, just 20-30 miles away. In the autumn, frost was reliably two or more weeks later on the Bay. Though we often think of the moderating effect of bodies of water in weather and climate, I want to use this experience as a bit of a re-framing. Specifically, the role of the Chesapeake Bay in autumn and winter is to warm the air. The effect is large enough that it matters to the people within a small number of miles of the shore. This is a case where the water had been accumulating heat all summer. Then in fall, when the air temperature fell below the water temperature it became a source of heat to the air. A really neat thing was to walk into a rough bay or river in late October and early November and feel how warm it is. (Rough needed to mix the warmer, deeper water, with the cooler water at the surface.)

The point here, there were situations when the heat in the water, in concert with the contrast between air temperature and water temperature, the heat from the water starts to warm the atmosphere. Look around and you can find examples on this at many different spatial sizes on many different spans of time. In a paper with my student Evan Oswald, we found that on hot days in Detroit, the presence of Lakes Huron, St. Clair and Erie kept downtown Detroit cooler than the inland suburbs in the hot part of the day, but warmer at night. Again, here is a moderating perception to people, caused, in part, by the water heating the air at night when the air temperature was low.

Let’s take this to the global scale. Energy comes from the Sun and heats the Earth. Our “extra” carbon dioxide holds a little more of that energy near the Earth’s surface than compared to, say, a 100 years ago. Some energy goes to heat the land surface and the air. Energy goes into melting ice – sea ice, glaciers and ice sheets. Most of the energy goes into the ocean, increasing the heat content of the ocean. Though most of the energy goes into the ocean, because of the large mass of the ocean, the mixing of ocean, and relative to air, the large specific heat, the temperature of the ocean takes a long time to increase. In this way the ocean actually moderates the air temperature – or, without the ocean, the Earth would be heating up a lot faster. Alternatively, the ocean is taking heat from the atmosphere. (Without the ocean, we also would be less likely to have things like The whole silly warming pause, warming hiatus thing.)

We are already seeing now, in 2014, how a relatively small change in the ocean surface temperature related to a weak, almost El Niño is leading to record surface air temperatures. This is a case of the ocean heating, relatively to last year, the atmosphere. In fact, reaching back to Ocean Hot and Hotter Still, I cite “Oceanic influences on recent continental warming,” that appeared in Climate Dynamics. This paper concludes that much of the “recent warming” observed on land can be traced to heating from the ocean. "Recent" in this paper is, more or less, the last half of a century, fifty years. The authors trace the heating of the land to increases of heat in the ocean.

I have tried to establish an intuitive and experience-based demonstration of the role of large bodies of water in the determination of air temperature. I have described an example, my experience at the coast during autumn, where as the heating by the Sun decreases, the heat from the water serves to warm the air. On a global scale, we are at this very moment living the fact that warming water in eastern Pacific Ocean is pushing the global-average surface (air) temperature to record highs. Therefore, it should logically follow that if we were to stop our emissions of carbon dioxide, thereby stopping the increase of energy being held at the Earth’s surface, that the energy being stored in the ocean will serve to heat the air and continue to warm the Earth’s average surface temperature, until a balance is reached.

I want to end by introducing the role that Point of View plays. Because we are most interested in how climate affects us, we are most interested in the surface air temperature, especially over land. You can imagine, that if you were in space studying the Earth, rather than surface air temperature being your primary focus, you might focus first and foremost on what is happening in the ocean. We would, then, not think so much of the ocean’s ability to heat the air, to increase the average surface temperature. Rather you would think of all of the heat stored in the ocean maintaining the planet in a more or less stable climate, with fluctuations in air temperature. Then the air temperature could be viewed as a low heat capacity envelope around the ocean that amplifies ocean temperature variability. Then, in our thought experiment of the carbon dioxide emissions halting, we would be seeing the atmosphere catching up with the more stable, perhaps more important ocean. It is our presence, our point of view, that makes the surface air temperature the important parameter, that frames our thinking of the ocean catching up and “heating” the planet.

Have a look at What would happen to the climate if we stopped emitting greenhouse gases today?


Figure 1: Simple Earth 3: Some basic ingredients of the Earth’s climate. There is heat going into the ocean. Ultimately, there is exchange of heat between the ocean and atmosphere. The same amount of heat in the atmosphere has a larger impact on temperature, than in the ocean. (This is simple Earth, so this is vastly over simplified heat transport.)
Categories:Climate Change

California Drought, El Niño, Warm Earth (One more time)

Published: December 5, 2014
California Drought, El Niño, Warm Earth (One more time)

Addition 12/10: Another Storm Coming to California. This is good.

This is the next in my series of El Niño updates. Previous entries

May 2014, Tracking El Niño and Underlying Models.
July 2014, Tracking El Niño: Summertime Update.
October 2014, El Niño, California Drought, and Predictions

In November I got some nice attention from the New Yorks Times, which I hoped would establish me as the Nate Silver of El Niño, but so far I have had no contract offers from ESPN. For those who need it, there are links to basic information such as definitions of terms in the earlier blogs. A new communication on El Niño from NCAR has links to a glossary.

It is raining in California, perhaps it is even perfect rain. With apologies in advance:

Perfect rain, perfect rain
Perfect rain, perfect rain
If you know what I'm singing about up here
C'mon, raise your hand

When the rain started I was immediately put in mind of the year 1999. I was living in the East at the time, and as I recall there was a drought. Then in September of 1999 Hurricane Floyd settled into North Carolina with rain that exceeded a 500-year event. Then in 2007 there was drought in Georgia, which as I recall was ultimately ended with a whole lot of rain. (Economic Impact of 2007 Drought) These past events lead us to “just in the nick of time” there is a savior. Perhaps that is the thinking here.

OK – California and El Niño: In the previous blog of this series, I said that I would be preparing for continued drought in California. This first rainstorm provides much needed and valuable water. It is not drought breaking, and recall that the California water system reaches across the western half of the country through the Colorado river basin. It will require rain and snow of great amounts and extending across large spatial domains to provide more than band-aid relief. It will take time to restore that part of the groundwater that can be restored. Worth remembering that earlier in 2014 there was also rain in California, for example, Jeff’s Masters February 14, Pineapple Express Bringing Significant Rains to Drought-Stricken California.

Most winter precipitation comes to California in discrete events. This figure, taken from Jeff’s blog (above), shows one of these events.

Figure 1. Total precipitable water (TPW) for Thursday, February 6, 2014. TPW is how much rain (in inches) would fall at a given location if one condensed out all of the water vapor in a column above the location into rain. For reference, 1 inch = 25.4 mm. A narrow “Atmospheric River” of moisture is seen extending from the subtropics near Hawaii into California. Image credit: University of Wisconsin SSEC.

These events are called atmospheric rivers, and local to the western part of the U.S., the Pineapple Express (really a nice article in Wikipedia - you might contribute to them while you are there). There are two points to make. The first point is to notice the narrowness of the stream of water vapor that is carried to the continent. The second point is that during an El Niño, atmospheric rivers are more likely to occur. As the February 2014 event shows, El Niño is not required for an atmospheric-river event. Likewise, El Niño does not assure atmospheric rivers. Drought breaking or even significant drought relief would occur, most likely, through a succession of atmospheric river events , which span the coastline from southern California up through the Northwest. Such a succession of events is observed, preferentially, with El Niño. So my analysis remains the same. If I have small farm near Cloverdale, California, and if I were looking to the skies for water, I would be preparing for continued drought. And very thankful for the water received, and thinking of how to use it best.

Returning to atmospheric rivers being narrow, when the stream of wet air gets to the coast two things happen. One, the air lifts and cools and precipitation happens, often a lot of it. Two, the weather system spreads along the mountains, much like a wave breaking on a beach. Therefore the spatial extent is greater than the narrow river of moisture brought to the continent. Still, however, precipitation is brought to the region in localized and discrete events. One event does not cover it all. There needs to be rain in the inland watersheds, and it is a good thing to be stored as snow in the mountains. Not all of the rain ends up being immediately available for drought relief.

Now turning to the El Niño forecast, first, using the products I have found to be the clearest and most usable (Australian Bureau of Meteorology). The latest Australian forecast is an El Niño Alert. In April-July of 2014 the level was Alert, which was reduced to a Watch in August – October, The level returned to Alert in November. In the December 2, 2014 update “The El Niño–Southern Oscillation (ENSO) Tracker status remains at El Niño ALERT level. Given current observations and model outlooks, the chance El Niño will be declared in the coming months remains at 70%, triple the average likelihood of an event occurring.”

As we have learned in this series, there is sharing of models and data across the centers. The analysis varies, but is in general consistent. The December 4, 2014 synopsis from the U.S. Climate Prediction Center is “There is an approximately 65% chance that El Niño conditions will be present during the Northern Hemisphere winter and last into the Northern Hemisphere spring 2015.” And further, “Similar to last month, most models predict SST anomalies to be at weak El Niño levels during November-January 2014-15 and to continue above the El Niño threshold into early 2015. Assuming that El Niño fully emerges, the forecaster consensus favors a weak event. In summary, there is an approximately 65% chance of El Niño conditions during the Northern Hemisphere winter, which are expected to last into the Northern Hemisphere spring 2015.”

Next, looking at the Australian ENSO Wrap-up from December 2, 2014. “Many climate indicators remain close to El Niño thresholds, with climate model outlooks suggesting further intensification of conditions remains likely. The Bureau’s ENSO Tracker status is currently at ALERT, indicating at least a 70% chance that El Niño will be declared in the coming months. Whether or not an El Niño fully develops, a number of El Niño-like impacts have already emerged.” And further, “If an El Niño is established, models suggest it will be weak, or moderate at most.”

This week’s rainstorm in Southern California might be viewed as an “El Niño-like impact.” With a strengthening of El Niño, it is reasonable to expect more storms, and more relief from the drought. Still, if I had that farm in California, I would be planning for drought and hoping to enjoy some rain. (Addition 12/10: Another Storm Coming to California. This is good.)

Returning one more time to my entry from May 29, 2014 , when I wrote, “even a moderate El Niño this year is likely to lead to the hottest year on record.” My rationale for this statement is that we are living in the hottest decade since we have had easily defended direct temperature measurements. We have remained warm, globally, despite relatively cool temperatures in the eastern Pacific. Given the importance of the eastern Pacific to the global picture, even a small break in the cool pattern is likely to lead to globally historic highs. Let’s do a summary, since modern temperature records began in 1880:

April 2014 the warmest April
May 2014 the warmest May
June 2014 the warmest June
July 2014 not quite the warmest July
August 2014 the warmest August
September 2014 the warmest September
October 2014 the warmest October (graph)

And from the World Meteorological Organization 2014 on course to be one of hottest, possibly hottest, on record - Exceptional heat and flooding in many parts of the world. Of course to make things interesting we’ve had some nice cold weather in the U.S. recently. Commenters: get ready.

A quick summary. If you read the previous blogs and quotes from the forecast and analysis centers, the El Niño forecast has been quite consistent from the beginning, and at this point, it looks like it will be quite a good El Niño forecast.


Forecast and Analysis Centers

Climate Prediction Center Alert System and the Climate Prediction Center Diagnostic Discussion

International Research Institute Forecast Products and the Quick Look

Japanese Meteorological Agency El Niño Monitoring and Outlook and a nice graph of historical events

Australian Bureau of Meteorology Wrapup

Netherlands Meteorological Institute (KNMI) Forecasts

Information Portals

CLIVAR (Variability and predictability of the ocean-atmosphere system) Forecast Page

World Meteorological Updates

Pacific Marine Environmental Laboratory El Niño Theme Page Forecasts

Climate Prediction Center FAQ

NOAA’s El Niño Page and NOAA’s La Niña Page

Summaries in Blogs

Judy Curry El Niño Watch


Rood’s Just Temperature Series

Just Temperature 3

Just Temperature 2

Just Temperature 1

Essay on Need to Adapt

Published: December 1, 2014
Essay on Need to Adapt

The Earth is warming, sea levels are rising, and the weather is changing. We know that the Earth has warmed and will continue to warm due to the carbon dioxide we are releasing into the atmosphere by burning fossil fuels—and the warming is and will be disruptive. Five years ago the talk was “if” we limited the increase in the average surface temperature of the Earth to 2 degrees Celsius, then we would avoid “dangerous” climate change. It is now quite obvious that we see large, consequential, and disruptive changes with even less warming—for example in the melting of the Arctic Sea ice. The commitments the world has made have us on a path toward 3.5 degrees of warming or more. If we burn all our fossil fuels, the warming will be much greater.

We have no choice but to adapt to this warming world. We have adapted to changes in the climate for the past 10,000 years—it is something we do. Now, scientific investigation has given us a vision of the future that is credible and actionable. This is unprecedented in history, and it gives us the opportunity to take responsibility and plan to adapt. We know that the Earth will warm; we know it will warm fast. We also know that the weather will change, and when the weather changes the way rain and snow are distributed will be different.

To take advantage of this knowledge, we need to think through scenarios of what will happen to real places. We need to look at the impact of rising sea level on the Sacramento River Delta, Norfolk and New York. We need to focus on how much water is stored in the snowpack of the Sierra Nevada and drought impacts on the forests, grasslands, and rangelands. We must move away from sweeping statements about more droughts and greater floods and instead play out the scenario and the cost of this warmer world to people. We must think of the impact of present climate events as lessons for the future. We need to start put together regional and national strategies, rather than patching different strategies together as fragmented responses of emergency management.

Should we just adapt—and not worry about our continued emissions of our energy waste into the atmosphere, ocean, and land? What would be adapt to? We started talking about the “new normal” when we calculated, in 2011, the 30-year average of temperatures from 1981 to 2010, and a new, warmer average “replaced” the 30-year average of some earlier period. In 10 more years we will have the next warmer “climate,” then the next, and the next—the “next normals.” There is no new normal. And the warming will be speeding up. There is no “just adapting” to this; there is no stable climate to adapt to. We must manage and limit our carbon dioxide waste or we will still be chasing the “new normal” in a thousand years.

It won’t just be getting warmer. Ecosystems will have to adapt far faster than they did in the past 10,000 years. After fires and droughts, trees will be trying to grow in a new and ever-changing climate. Intrusion of the sea into the Sacramento Delta will make Katrina in New Orleans seem like a quaint artifact of the “old normal.” The accelerated release of methane and carbon dioxide as the Arctic melts will accelerate the warming. The oceans will become acidic, and there will be vast changes to phytoplankton and zooplankton. The oceans will become warm and will release the carbon dioxide we take comfort in their storing. There is no “just adapting.” We will be required to adapt, and the rate of change will make adaptation ever more challenging. We need both aggressive reduction of greenhouse gas emissions to mitigate the future changes, and we need aggressive adaptation to cope with the changes already occurring and those that are in store.

U.S. Lightning Strikes May Increase 50% Due to Global Warming

Published: November 14, 2014
A warmer world will have much more dangerous cloud-to-ground lightning capable of igniting more forest fires, according to a study published Thursday in the Journal Science. The research found that for each degree Centigrade (1.8°F) of global warming, lightning in the U.S. is expected to increase by 12%. This would result in about a 50% increase in lightning by the year 2100, assuming business-as-usual emissions result in a world that is 4°C (7°F) warmer. Main author David Romps of the University of California-Berkeley said in a press release, “This has to do with water vapor, which is the fuel for explosive deep convection in the atmosphere. Warming causes there to be more water vapor in the atmosphere, and if you have more fuel lying around, when you get ignition, it can go big time…the faster the updrafts, the more lightning, and the more precipitation, the more lightning.” The study looked at U.S. lightning statistics for the year 2011, and discovered that a simple measure of atmospheric heat and moisture--the precipitation rate multiplied by the stability of the atmosphere (expressed as the Convective Available Potential Energy, or CAPE)--could describe 77% of the variation in lighting. By applying this simple measure to predicted levels of heat and moisture in a future warmer world, the scientists came up with their predictions for more lightning. The study makes sense from basic principles, and brings up three major concerns about the impacts of a future world with more lightning:

1) More lightning-caused fires
2) More lightning-caused ozone pollution and thus global warming
3) More lightning direct strike deaths and damages

Figure 1. Lightning sparks a grass fire near Granite, Oklahoma on June 8, 2008. Image credit: wunderphotographer Glenn Patterson.

The costs and death toll from lightning-caused fires in the U.S. and Canada
Over the ten years from 2003 - 2012, 42 U.S. firefighters were killed as a result of lightning-caused fires. An additional 19 firefighters were killed by the lightning-caused Yarnell Hill Fire in Arizona in 2013. U.S. wildfire fighting costs averaged $1.8 billion annually during 2009 - 2013, according to Headwaters Economics. Although only 15% of U.S. wildfires were ignited by lightning between 2001 - 2010, these accounted for approximately 60% of the acres burned, and much of the annual costs of firefighting, according to the National Interagency Fire Center. For example, in 2012, the Whitewater-Baldy Complex Fire, the largest fire in New Mexico history, and the Rush Fire, the 2nd largest in California history, were both triggered by lightning strikes. Lighting also causes building fires through direct strikes. The National Fire Protection Association says that lightning-caused fires that are responded to by local fire departments in the U.S. killed an average of nine people per year and did $451 million in direct property damage per year between 2007 - 2012.

Environment Canada estimates that lightning strikes are responsible for 45% of all wildfires in Canada and 81% of the total area burned. The cost of lightning-related damage and disruption to the Canadian economy was estimated to be between $600 million and $1 billion each year (Mills et al. 2009).

Figure 2. Smoke rises from the uncontrolled northern front of the lightning-ignited Gap fire on July 5, 2008 near Goleta, California. President Bush declared a state of emergency for all of California in July 2008 in response to more than 1,400 fires that were mostly started by dry lightning storms on June 20, 2008. More than 19,000 firefighters from 42 states battled the California wildfires. (Photo by David McNew/Getty Images)

Death and damages due to direct lightning strikes
In addition to killing people in lighting-caused fires, lightning kills people with direct strikes. In 2006 - 2013, an average of 33 people per year died as a result of lightning strikes, according to NOAA. So far in 2014, 25 people have been killed. Fishing, camping and boating were the three highest risk activities for people dying from lightning strikes, according to a 2013 NWS study. The insured costs of direct lightning strikes have been rising in recents years, due to an increase in valuable home electronics that get fried in a strike. These damages were approximately $1 billion per year in 2010 - 2011, according to the Insurance Information Institute.

Lightning-caused forest fires may increase at a lesser rate
Climate models show that the increase in instability (higher CAPE) due to global warming is not expected to be uniform over the U.S., with strong increases over the Southeast U.S., and little increase over the Western U.S., where the majority of lightning-caused fires originate. The 12% increase in lighting per °C of global warming the study found is averaged over the entire U.S., and the increase in lightning is likely to be much lower over the Western United States--perhaps a factor of six less. A 2007 study by Del Genio et al. found that increasing the global temperature by 2.7°C would cause drying over the Western U.S. that would lead to fewer thunderstorms overall. However, the strongest thunderstorms increased in number by 26%, leading to a 6% increase in the total amount of lighting hitting the ground each year, or about a 2% increase per °C of global warming.

Increased lightning will create more ozone pollution and more global warming
Lightning creates nitrogen oxides, which in turn react to make significant amounts of ozone in the lower atmosphere--a dangerous pollutant that seriously impacts human health and crop growth. Ozone is also a greenhouse gas, so global warming-caused increases in lightning could potentially cause additional global warming of a few percent. How much is uncertain, as estimates of lightning-produced nitrogen oxides vary by up to a factor of four. Lower-atmosphere ozone was responsible for about 12% of human-caused global warming due to greenhouse gases in 2011, according to the 2013 IPCC report. However, increased ozone due to lightning could be offset somewhat by the fact that lightning-created nitrogen oxides trigger chemical reactions that help destroy methane, another potent greenhouse gas.

Video 1. ‪Every Lightning Strike in America in 2011, In One Minute‬. Data from the National Lightning Detection Network, UAlbany; animation by David Romps, UC Berkeley, and Phil Ebiner, UC Berkeley Public Affairs. Thursday's study in Science studied lightning over the U.S. in 2011 to come up with a simple way to represent lightning frequency based on how much heat and moisture is in the atmosphere.

Jeff Masters
About the Blogs
These blogs are a compilation of Dr. Jeff Masters,
Dr. Ricky Rood, and Angela Fritz on the topic of climate change, including science, events, politics and policy, and opinion.