Human Influence on Weather/Climate Chapter 18 material

Well-Accepted Ideas (IPCC) –Human activites causing a rapid rise in atmospheric CO 2  Fossil fuel burning  Destruction of forests –Human activities have destroyed a significant amount of stratospheric ozone –Higher global temperatures have correlated with increasing CO 2

Land Use Changes  Dust Bowl –Prairie grass was plowed under and overgrazed –With no grass to hold the soil in place, a naturally occurring prolonged dry spell (drought) caused the bare soil to be carried away by the wind  Owens Lake

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

The Urban Heat Island: The Ultimate Land Use Change  Localized climate change –Increased runoff = warmer daytimes (less cooling due to evaporation) –Increased surface area = more solar radiation can be absorbed, more IR emitted and re- absorbed at night –Autos, factories, people = heat

Stratospheric Ozone Depletion –Ozone is good or bad, depending upon where it is  Good: In the stratosphere, where it protects us from much of the sun’s harmful ultraviolet radiation, which causes skin cancer  Bad: In the troposphere, where we are - it is toxic to plants, animals and us

‘Ozone Hole’ –CFCs (chlorofluorocarbons) destroy ozone very efficiently, used in many things in 20 th century –Ozone “hole” is an area over the south pole where stratospheric ozone levels have drastically fallen –Atmospheric conditions (extreme cold, polar vortex) lead to efficient ozone destruction there

An international environmental positive  Have been banned and atmospheric CFC levels are leveling off (1987)  As atmospheric CFC levels decline, stratospheric ozone should recover, but there is a significant delay between CFC reduction and ozone recovery

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

Enhanced Greenhouse Effect  “Global Warming” –Too much of a “good” thing –Anthropogenic (human-induced)  CO 2  Methane  CFCs – low concentrations, but very efficient IR absorbers (replacements of CFCs also very efficient IR absorbers)  So the earth is warming on average…what does that mean?

Global Warming: Uncertainties  JUST A FEW OF THE POTENTIAL EFFECTS  Cloud cover: Should increase as condensation nuclei (pollution) increase, but type of cloud has an effect on surface temperature. Some cause cooling, some cause warming. Which type will increase more??  Sea Level changes: Expected to rise as snow/ice melts, and is happening now, but some regions will see increased snowfall if planet warms, offsetting some, if not all, of the sea level rise  Ocean Currents: Infusion of fresh water alters density, disrupts currents

Global Response?  Climate change: Gradual or Rapid?  Political Forces –Will countries play by the rules after ratifying a treaty? (Canada) –Should developed countries curtail their emissions and let developing nations continue until their emissions become “substantial?” –Should developing nations be denied the chance the U.S. and other developed nations had?  No, it’s only fair. We can’t stifle their development  Yes, we know more today about what we’re doing to the planet –Then, should developed nations cover the increased cost developing nations will incur to meet stricter environmental guidelines? After all, we screwed it up in the first place.

What do ya’ll think?  Is this just liberal fear-mongering BS?  Something you’re concerned about?  Something you’re willing to sacrifice for to deal with? (higher energy prices, etc.)