Human Influence on Weather/ClimateHuman Influence on Weather/Climate Certainties:Certainties:

– We are causing a rapid rise in atmospheric COWe are causing a rapid rise in atmospheric CO22

Fossil fuel burningFossil fuel burning Destruction of forestsDestruction of forests

– Cities are warmer, on average, than their suburbsCities are warmer, on average, than their suburbs Urban Heat IslandUrban Heat Island Increased emission of heat (cars, people)Increased emission of heat (cars, people) Changes in water cyclingChanges in water cycling Changes in surface area and Changes in surface area and

heat capacityheat capacity

– We have destroyed a significant We have destroyed a significant amount of stratospheric ozone amount of stratospheric ozone

– Higher global temperatures have Higher global temperatures have correlated with increasing COcorrelated with increasing CO22

Caution! Know Your Axes!Caution! Know Your Axes!The perceived slope of a graph means less than you might think!The perceived slope of a graph means less than you might think!

-- Scale of Y-Axis

-- Maximum slope with small range

-- Minimum slope with large range

-- What would graph to left look like if the scale was from 0 to 400?

-- Scale of X-Axis

-- Same idea- spread it out, decrease the slope

Be sure you’re comparing “apples to apples” when looking at more than one graph!

Land Use ChangesLand Use Changes The Dust BowlThe Dust Bowl

– Prairie grass was plowed under and overgrazedPrairie grass was plowed under and overgrazed– With no grass to hold the soil in place, a naturally occurring With no grass to hold the soil in place, a naturally occurring

prolonged dry spell (drought) caused the bare soil to be prolonged dry spell (drought) caused the bare soil to be carried away by the wind; lack of wind breaks (trees)carried away by the wind; lack of wind breaks (trees)

The Middle EastThe Middle East– Biblical reference to the tall cedars of LebanonBiblical reference to the tall cedars of Lebanon– Forests cut down, water cycling changedForests cut down, water cycling changed

Trees/plants retain water, so more runs out of local areaTrees/plants retain water, so more runs out of local area Transpiration: release of water vaporTranspiration: release of water vapor

by plants is by plants is reduced; waterreduced; water

cycle alteredcycle altered

The Urban Heat Island: The Ultimate The Urban Heat Island: The Ultimate Land Use ChangeLand Use Change

Localized climate change: T (city) > T (rural)Localized climate change: T (city) > T (rural)– Water Cycling: Increased runoff = warmer daytimes Water Cycling: Increased runoff = warmer daytimes

(less cooling due to evaporation)(less cooling due to evaporation)– Increased surface area = more solar radiation can Increased surface area = more solar radiation can

be absorbed, more IR emitted and re-absorbed at be absorbed, more IR emitted and re-absorbed at night; also higher heat capacity night; also higher heat capacity building materials

– Autos, factories, Autos, factories, people emit heatpeople emit heat

Ozone Depletion: Why We CareOzone Depletion: Why We Care Ozone protects us from high-energy (short Ozone protects us from high-energy (short

wavelength) wavelength) UV radiation from the sunfrom the sun Measured in Measured in Dobson Units. Decreases in ozone will . Decreases in ozone will

cause increases in skin cancer, and ozone levels have cause increases in skin cancer, and ozone levels have generally been generally been decreasing..

Ozone Depletion: Why it’s HappeningOzone Depletion: Why it’s Happening Ozone is a highly toxic gas, which means it can be Ozone is a highly toxic gas, which means it can be

good or bad, depending upon where it isgood or bad, depending upon where it is Good: In the Good: In the stratospherestratosphere, where it protects us from much of the , where it protects us from much of the

sun’s harmful ultraviolet radiation, which causes skin cancersun’s harmful ultraviolet radiation, which causes skin cancer Bad: In the troposphere, where we are- it is poisonous!Bad: In the troposphere, where we are- it is poisonous!

Chlorofluorocarbons destroy ozone very efficientlyChlorofluorocarbons destroy ozone very efficiently

Ozone Depletion: There is HopeOzone Depletion: There is Hope CFCs destroy ozone very efficientlyCFCs destroy ozone very efficiently

– Destruction greatest in high latitudesDestruction greatest in high latitudes– Have been banned and atmospheric CFC levels Have been banned and atmospheric CFC levels

are leveling off are leveling off– As atmospheric CFC levels decline, stratospheric As atmospheric CFC levels decline, stratospheric

ozone should recover, but there is a ozone should recover, but there is a significant delay between CFC significant delay between CFC reduction and reduction and ozone recovery (~60 years)(~60 years)

Ozone Depletion: Ozone “Hole”: Ozone “Hole” Ozone “hole” is an area over the south pole where Ozone “hole” is an area over the south pole where

stratospheric ozone levels have drastically fallenstratospheric ozone levels have drastically fallen– Atmospheric conditions (extreme cold, polar vortex) lead to Atmospheric conditions (extreme cold, polar vortex) lead to

efficient ozone destruction: efficient ozone destruction: polar stratospheric clouds (PSC)– Winter/spring occurrenceWinter/spring occurrence– Not as dramatic over the Not as dramatic over the north north

polepole

A World Avoided…A World Avoided…

From Douglass, Newman & Solomon, The Antarctic Ozone Hole, an Update

Global Warming: The Global Warming: The EnhancedEnhanced Greenhouse EffectGreenhouse Effect

TheThe Greenhouse Effect Greenhouse Effect keeps our planet about 60F keeps our planet about 60F warmer than it otherwise would be. Life as we know it warmer than it otherwise would be. Life as we know it depends upon this effect. Greenhouse gases depends upon this effect. Greenhouse gases (primarily water vapor and carbon dioxide) absorb/re-(primarily water vapor and carbon dioxide) absorb/re-emit IR radiation.emit IR radiation.

Enhanced Greenhouse EffectEnhanced Greenhouse Effect is is “Global Warming”“Global Warming”– Too much of a “good” thingToo much of a “good” thing– AnthropogenicAnthropogenic (human-induced) (human-induced)

COCO22: correlates well with temp.: correlates well with temp. MethaneMethane CFCs – low concentrations, but CFCs – low concentrations, but

very efficient IR absorbersvery efficient IR absorbers

CHCH44, CO, CO22 and Global Temperature Trend and Global Temperature Trend

http://www.skepticalscience.com/co2-measurements-uncertainty.htm

http://www.skepticalscience.com/trend_and_variation.html

http://www.globalchange.gov/browse/multimedia/earths-temperature-variations

What about cooling I’ve heard about?What about cooling I’ve heard about?

Global Decadal TemperaturesGlobal Decadal Temperatures

http://arctic.atmos.uiuc.edu/cryosphere/arctic.seaice.2007.update.mov

GlobalGlobal Warming: Some UncertaintiesWarming: Some Uncertainties Cloud cover: Should increase as condensation nuclei (pollution) Cloud cover: Should increase as condensation nuclei (pollution)

increase, but increase, but typetype of cloud has an effect on surface of cloud has an effect on surface temperature. Some cause cooling, some cause warming. temperature. Some cause cooling, some cause warming. Which type will increase more? Climate models still struggle Which type will increase more? Climate models still struggle with cloud prediction.with cloud prediction.

Sea Level changes: Expected to rise as snow/ice melts, and as Sea Level changes: Expected to rise as snow/ice melts, and as water warms (and expands), and is happening now, but some water warms (and expands), and is happening now, but some regions will see increased snowfall if planet warms, offsetting regions will see increased snowfall if planet warms, offsetting some, but not all of the sea level risesome, but not all of the sea level rise– Recent dramatic cooling of top 2,500ft ocean layerRecent dramatic cooling of top 2,500ft ocean layer– More recent work on this ocean “cooling”More recent work on this ocean “cooling”– Island nations especially concernedIsland nations especially concerned

Ocean Currents: Infusion of fresh water alters density, disrupts Ocean Currents: Infusion of fresh water alters density, disrupts currents; local climate changes currents; local climate changes (warming (warming andand cooling) cooling)

Climate change: Gradual or Rapid?Climate change: Gradual or Rapid?– ““slipping” glaciers lubricated by meltwaterslipping” glaciers lubricated by meltwater

Sea Level RiseSea Level Rise

Thermal ExpansionThermal Expansion Icecaps and Glaciers (Greenland)Icecaps and Glaciers (Greenland)

GlobalGlobal Warming: Other UncertaintiesWarming: Other Uncertainties

Political ForcesPolitical Forces– Will countries play by the rules after ratifying a Will countries play by the rules after ratifying a

treaty? (Not happening for many countries now)treaty? (Not happening for many countries now)– Should developed countries curtail their emissions Should developed countries curtail their emissions

and let developing nations continue until their and let developing nations continue until their emissions become “substantial?”emissions become “substantial?”

– Should developing nations be denied the chance Should developing nations be denied the chance the U.S. and other developed nations had?the U.S. and other developed nations had? No, it’s only fair. We can’t stifle their developmentNo, it’s only fair. We can’t stifle their development Yes, we know more today about what we’re doing to the Yes, we know more today about what we’re doing to the

planetplanet– Then, should developed nations cover the increased cost Then, should developed nations cover the increased cost

developing nations will incur to meet stricter environmental developing nations will incur to meet stricter environmental guidelines? After all, we screwed it up in the first place.guidelines? After all, we screwed it up in the first place.

– Carbon credit tradingCarbon credit trading

And Finally…..And Finally…..

And finally, most important of all, basing an And finally, most important of all, basing an economy on a commodity that [in my economy on a commodity that [in my opinion] is controlled by the most backward, opinion] is controlled by the most backward, unstable, and violent countries in the world unstable, and violent countries in the world is madness. (2006, but still relevant)is madness. (2006, but still relevant)

- Craig Bohren, in - Craig Bohren, in USA TodayUSA Today Now we have fracking. So, is cheap energy Now we have fracking. So, is cheap energy

and the potential for energy independence and the potential for energy independence necessarily a good thing?necessarily a good thing?

Key Figures Key Figures

READ CHAPTER 18, it’s all importantREAD CHAPTER 18, it’s all important