Climate Change: Present and FutureHurricanes & Tornadoes

Some of chapters 19, 20 & 21Pete Kozich

Climate Change Factors

• Extraterrestrial factors: Solar output, Earth-Sun geometry,

Interstellar dust… focus on these first• Intra-Earth System factors: Atmospheric reflectivity (aerosols, clouds, and

precipitation) Surface reflectivity, Continental drift, Atmospheric chemistry, Volcanic emissions, Atmosphere-Ocean heat exchange, Mountain building

Climate Change

…already covered the extraterrestrial factors

Climate change

• Intra-Earth System factors: Atmospheric reflectivity (aerosols, clouds, and

precipitation) Surface reflectivity, Continental drift, Atmospheric chemistry, Volcanic emissions, Atmosphere-Ocean heat exchange, Mountain building

• Already covered the boldface• That leaves: Atmospheric reflectivity (aerosols,

clouds, and precipitation) Surface reflectivity, and Atmospheric chemistry

Climate Change• Surface reflectivity (surface albedo). Increased

albedo would lead to less surface warming, with more sunlight reflected into space. How does one increase surface albedo: more ice & snow, less oceans, more deserts.

• Atmospheric chemistry. N2, 02, and Ar do little to climate. H20, C02, and CH4 are important greenhouse gases. S04 helps facilitate condensation and ends up reflecting lots of incoming sunlight, and so would cool the surface of the earth.

Some estimates of

major factors

involved in climate change

Climate Change• Atmospheric reflectivity (aerosols, clouds, and

precipitation). This is the great unknown, and probably has even

greater impacts than greenhouse gases. Clouds comprise about 2/3 of Earth’s albedo, which clouds affecting radiation transfer depending on their level and thickness. Precipitation nuclei affect heating profiles and change cloud reflection properties. Precipitation also is important in latent heat release and surface properties of the Earth. It gets very confusing and extremely complex very quickly. The roles of water vapor are extremely complex in the atmosphere.

Climate• Clouds at upper levels tend to emit little energy

and allow a lot of sunlight through. Increase surface temp

Clouds at lower levels tend to emit a lot of energy but not allow much sunlight through.

Decrease surface tempClouds that are thicker and have more cloud

condensation nuclei reflect more. Also, how long clouds last will affect temperatures.

Sunspot cycles

• Shorter sunspot cycles (~10 years), more active sun and greater solar output. Last several decades.

• Longer period cycles (~12 years), less solar output (textbook has great picture of temperature and sunspot period). No sunspots during Little Ice Age.

• Is this as large of an effect or larger than greenhouse gases? Possibly, possibly not. We don’t know.

What to conclude• We are not certain what has caused global

warming the past few decades.• Greenhouse gases do seem at least partially

responsible for it. The sun is probably also at least partially responsible. Global warming is also occurring on Mars, though.

• Most global warming research has ignored the sun, Earth’s primary energy source. Our society has become too greenhouse gas obsessive. This will obsession will probably decrease a bit in the future, as I would guess we’ll all figure out that greenhouse gases are not the whole story.

Remember• Don’t forget about the oceans, cloud changes,

and changes in solar radiation in addition to greenhouse gas concentrations. All four play very large factors in our climate for time scales pertinent to our lifetimes. Vegetation changes may also be significant.

• We will probably know a great deal more than we do in 20 years. If the temperature trends shoot upward the next 20 years, as they did from 1980-2000, then we indeed have trouble and will need to address global warming more fully than we do now.

Hurricanes

• We do not know how climate change will effect hurricanes. Best predictions to date: near same or decrease in overall number, with the very strongest possibly becoming slightly stronger if global warming continues.

• We do not a lot more about formation, structure, and intensity of hurricanes than how they would change if the future climate changes appreciably.

Hurricanes• Formation. Necessary but not sufficient

conditions…-Disturbance of low pressure. Tropical wave, ITCZ

rollup, monsoon trough, stalled frontal boundary, MCS, midlatitude cyclone

-Low level cyclonic vorticity (spin)-Moist low and mid levels.-Vertical instability.-Planetary vorticity (not on equator)-Lack of vertical wind shear, with diffluent pattern

aloft.-Sufficiently warm ocean temperatures.

Hurricanes• Eye formation.Heating from deep clouds in tropical storm help

contract the wind field and change the vertical wind fields and structure as well. Eventually, the deep clouds will cause sinking motion over the middle of the storm. When that sinking motion is great enough, it will dissipate the clouds, making an eye, and some of that air will be ingested in the deep clouds surrounding the eye (the eyewall). The eyewall will intensify until it reaches equilibrium with the maximum intensity limits set on by its surrounding environment.

Devonian oxygen increasing

Tornadoes

• Storms with a persistent, rotating updraft (supercells) can have strong vertical winds. Evaporatively cooled air associated with falling precipitation may meet air ahead of it that is warm and rising. Interaction with the thunderstorm updraft (typically spinning cyclonically) may help create a violent, rotating column of wind in contact with the ground (a tornado).