Vertical structure of the atmosphere

Stratosphere ozone layer / ozone hole ultraviolet solar radiation sulfate aerosols from volcanic eruptions increasing GHG produces cooling Troposphere most clouds and atmospheric water vapor ozone from air pollution short residence time of aerosols

Hurricanes and other storms A taste of things to come? Keeping count: will there be more cyclones in the future? Surges and downpours Coastal concerns beyond the tropics Coastal storm flooding: a deepening problem Tornadoes: an overblown connection? What are the insurance companies thinking?

Was \ Hurricane Katrina related to global warming? Satellite image of Hurricane Katrina August 28, 2005. Intense hurricanes have well developed eyes like the one shown in this image.

Close-up of the eye of Hurricane Katrina.

Photo taken from a research aircraft flying through the eye of Hurricane Katrina. The photo was taken by a UW researcher. The deep clouds surrounding the eye are referred to as the eye wall.

2005 hurricane tracks. Far more storms made landfall than in a typical year.

Text 2005 hurricane tracks. Far more storms made landfall than in a typical year.

2005 hurricane tracks. Far more storms made landfall than in a typical year.

1991 Bangladesh cyclone: 144,000 fatalities 29 April 1991 Bangladesh cyclone. For further details, see Wikipedia.

El Niño La Niña Upper panels: Hurricane positions on the last day that they exhibit hurricane-force winds during the (a) 25 warmest and (b) 25 coldest years in terms of sea surface temperature in the equatorial cold tongue region (6 N-6 S, 180-90 W) based on the period of record (1886-2000). Lower panels: Daily hurricane and tropical cyclone positions during the (a) 10 warmest and (b) 10 coldest years in terms of sea surface temperature in the equatorial cold tongue regions based on the period of record (1949-2000).

Hurricane damage winds storm surges flooding

Winds

2005 hurricane tracks. Far more storms made landfall than in a typical year.

Winds

Storm surge

2005 hurricane tracks. Far more storms made landfall than in a typical year.

Flooding

Hurricane Katrina: Ocean Heat Content Track of Hurricane Katrina with estimated maximum wind speed indicated. Colored shading shows the heat content of the ocean, a measure of the vertically-averaged temperature, as measured by satellite altimeter. Sea level is about 15 cm (6 ) higher in the red areas than in the blue areas. The red band is known as the Florida loop current. It is an extension of the current of warm water that comes up from the tropics and feeds into the Gulf stream The configuration of the loop current changes from week to week. It was very prominent during the disastrous 2005 hurricane season. Hurricanes Katrina intensified to Category 5 as they passed over the loop current and then weakened to Category 3 as they passed over the cooler waters closer to the coast.

Hurricane produce oceanic upwelling beneath the eye Upwelling of cold water can provide a strong negative feedback that limits the strength of the hurricane. Modeling results: from www.gfdl.noaa.gov/.../ glob_warm_hurr.html

but in the loop current the warm water extends through a deep layer. Hence, the upwelled water is warm, and the negative feedback is minimal. Track of Hurricane Katrina with estimated maximum wind speed indicated. Colored shading shows the heat content of the ocean, a measure of the vertically-averaged temperature, as measured by satellite altimeter. Sea level is about 15 cm (6 ) higher in the red areas than in the blue areas. The red band is known as the Florida loop current. It is an extension of the current of warm water that comes up from the tropics and feeds into the Gulf stream The configuration of the loop current changes from week to week. It was very prominent during the disastrous 2005 hurricane season. Hurricanes Katrina intensified to Category 5 as they passed over the loop current and then weakened to Category 3 as they passed over the cooler waters closer to the coast. Hence, tropical storms tend to intensify when they pass over features like the loop current.

Hurricane Katrina Sea Surface Temperature Track of Hurricane Katrina. In this slide the colored shading shows sea surface temperature. The blue patches are colder water from well below the surface that upwelled to the surface as the hurricane passed. The loop current doesn t show up clearly in the sea surface temperature distribution.

Is hurricane damage increasing? Statistics based on inflation-adjusted dollars show an increase over the 20th century but skeptics have been quick to point out that the number of people living in harm s way and the value of the property that is vulnerable to hurricane damage is also increasing. When the damage statistics are divided by tangible wealth, the trend virtually disappears. Damaging hurricanes are such rare events that trends have little meaning.

The hurricane controversy Judith Curry Georgia Tech William Gray Colorado State University Kerry Emanuel MIT Christopher Landsea NOAA/AOML Miami

From recent paper of Webster, Holland, Curry and Chang http://shadow.eas.gatech.edu/~kcobb/energy/readings/webster05.pdf

Chris Landsea

Are hurricanes becoming more intense? Kerry Emanuel PDI stands for power dissipation index a measure of the cube of the maximim wind speed for each day, integrated over the lifetime of each hurricane, summed over all the hurricanes for each year. This is a much more robust estimate of the intensity of hurricanes than numbers of Category 4/5 storms or hurricane damage. This graph shows that PDI is highly correlated with sea surface temperature along the track of the major storms. Hence, if sea surface temperature rises in redsponse to global warming it can be inferred that the PDI, a measure of hurricane intensity, will continue to rise.

Should we expect that hurricanes will become more intense? Based on numerical simulations of ideal. For further details, see www.gfdl.gov/~rt/ glob_warm_hurr.html

Can individual hurricanes like Hurricane Katrina be attributed to global warming? No Can it be said that global warming made an individual hurricane like Hurricane Katrina stronger than it would have otherwise been? Not a good way to frame the question. Confuses climate and weather. Are hurricanes becoming more intense? The evidence is suggestive, but not conclusive at this point. Should we expect that hurricanes will become more intense? Yes. Heavier rains, stronger winds, stronger storm surges. Based on numerical simulations of ideal. For further details, see www.gfdl.gov/~rt/ glob_warm_hurr.html

More intense storms in the Arctic?

Polar lows Tight, intense cyclones like these sometimes develop over the Arctic Ocean and the surrounding polar seas. Like tropical cyclones, they require open water to intensify. They are not as intense as tropical cyclones but they can produce small storm surges that cause damage to low lying coastlines. The occur most often in autumn, just before the surface of the ocean freezes.

Erosion is a problem, even in todays climate prospect of more intense storms less dependable protection from sea ice

More tornadoes? Sequence of images from the life cycle of an individual tornado over Nebraska. This photos and the ones on the next three slides are from J. M. Wallace and Peter V. Hobbs, Atmospheric Science, An Introductory Survey, Academic Press. Photos courtesy of Kathryn Piotrowski.

Tornadoes develop as an integral part of supercell thunderstorms... intense, long lasting storms that develop rotation. These storms develop only under certain very special conditions. The US Great Plains is one of those places. They derive their energy from the release of latent heat when water vapor condenses in intense updrafts.

Will global warming bring more tornadoes? Same issues as with hurricanes Hard to prove the existence of a trend, but there s reason to believe that storms that derive their energy from the release of latent heat with the condensation of water vapor will be more intense in a warmer world with more atmospheric water vapor.