Weather climatestehrmay2011

-- of a small rock in space

Jeffrey W. Stehr, Ph.D.University of MarylandAtmospheric & Oceanic ScienceWith contributions fromJohn S. Perry, Ph.D.

May 24, 2011

Weather and Climate

Shameless Self-PromotionUniversity of Maryland now has a professional

masters program!

And an undergraduate program is on its way!

Your son/daughter/self will be able to go from a high school diploma to a professional masters in 5 years.

All our graduates get jobs in their chosen fields.

You’re looking at the new associate director of both.

General Plan for our HourWhy our rock has a nicer climate than most rocks

What determines the climates of our rock

The distribution of climates, and where Virginia fits

How weather arises in all its diversity

How weather predictions come about

How all this is changing, and what we humans have done

Overall Goal: To equip YOU with the basic understanding you will need as a Virginia Naturalist.

2010: Global Temperatures

Global Top 10 Warmest Years (Jan-Dec) Anomaly °C Anomaly °F2010 0.62 1.122005 0.62 1.121998 0.60 1.082003 0.58 1.042002 0.58 1.042009 0.56 1.012006 0.56 1.012007 0.55 0.992004 0.54 0.972001 0.52 0.94

The 1901-2000 average combined land and ocean annual temperature is 13.9°C (56.9°F), the annually averaged land temperature for the same period is 8.5°C (47.3°F), and the long-term annually averaged sea surface temperature is 16.1°C (60.9°F).

Surf for yourself!NOAA’s climate Web site

http://www.ncdc.noaa.gov/sotc/

IPCC Web site:

http://www.ipcc.ch/

Climategate: Proof! (of what?)

Himalayan glaciers will not melt by 2035 (~90% receding) IPCC has printed a retraction IPCC didn’t follow their own rules in allowing a non-peer-reviewed

source to come into its writing

Phil Jones has a tough job, is human, spends a fair bit of time responding to skeptics

No evidence of a trick, but some trouble… In scientific parlance, “trick” means “a clever method”, not an attempt

to deceiveProblems with the tree-ring data, yes.

Allegations that a peer-reviewed article was kept out of the IPCC report were false.

Climategate: good stuffClimate researchers will be more open about

their data and methodsThis is very, very good for science

Note: two much more thorough investigations have still found nothing more

A Rock in Space (Moon)

Max: 123°C

Min: - 233°C(*or -243°C?)

Not a nice place!

Another bad rock: Mars Thin atmosphere 0.7%

Earth’s (95% CO2)

Little water

CO2 frozen in ice cap

Very cold

Little to no greenhouse effect

Min: -140°C

Max: 20°C

Average: -63°C

Another Bad Rock: Venus THICK atmosphere, 92x

Earth’s (96% CO2, 3% N2)

Mean surface Temperature: 482°C

Sulfuric acid clouds

Runaway greenhouse effect

No oceans

Little water

Radar composite of Venus

Our Rock in Space

Much nicer!What’s different?

•Water•Green stuff•Air! – Our Atmosphere

Our AtmosphereNot much of it – half below 4 miles

Many gasesMostly N2, O2, Ar

Variable:Water vaporCarbon DioxideMethaneOzone

Made by life (the dynamic gases) and vital for life

Our Atmosphere and our Sun

•Sun’s heat mostly in the visible, where the atmosphere is transparent.•Earth’s heat radiation is in the infrared, where trace gases absorb much of it.•The most important absorbing gases are water vapor and carbon dioxide.•These gases absorb about 90% of the heat radiated by the Earth.•This was clearly understood by 1847.

The “Greenhouse Effect”

•Average temperature without greenhouse gases:

2 °F•Average temperature with greenhouse gases:

59 °F

More GHG = More Heating

Natural Climate Changes: Ice Ages

Winter vs. summer: Earth tilts toward the sun in summer, away from it in winter

Earth’s orbit is an ellipse, not a circle. Earth is closer to the sun in NH winter, farther away in NH summer…this changes.

What changes:Timing of the closeness vs. tilt: precessionThe tilt itself: obliquityOval vs. circular shape of the orbit: eccentricitySolar output

Where axispoints when

Tilt of axis

“Ovalness” of orbit

What about right now?We’re actually in a very quiet period

Little eccentricity

Closer in NH winter, farther away in summer (most of the land is here)

Should be gentle warming for next 25,000 years

No cooling sufficient to cause an ice age in next 50,000-100,000 years

Our Rock under the Greenhouse

General Circulation and Climate

•Circulation driven by heating in tropics and cooling near poles•Rotation of the Earth forces breakup into three major cells.•These cells determine the general distribution of climates over the planet.•Mountains, configuration of continents, ocean currents influence the details.

Climates of the Planet

Recipe for ClimateA nice, hot Sun (but not too hot)

A comfortable orbit (right distance, nearly circular)

Reasonable rotation at a moderate inclination (day not too long, inclination not 90°)

An atmosphere with a good assortment of heat-absorbing gases (some greenhouse)

An assortment of oceans and land masses with varied topography. (land not all in one place)

Weather

Species of turbulence – “Weather”

How do we predict weather?

What’s happening now?

Global network of surface observing stations

Upper Air Observations (weather balloons)

Weather satellites

Geostationary satellites

Polar-orbiting satellites

Assimilate Data and Analyze

Numerical Forecast Model• Basic equations

• Many approximations

• Clever numerical methods

• Supercomputers

Numerical Forecast

Numerical Forecast

Numerical Forecast

Numerical Forecast

Numerical Forecast

The #@$% weather-guessers never get it right!

Forecasts are better than ever!

How can we predict climate if we can’t predict the weather?

The same way we can predict the tide but not the individual waves

Climate prediction through the ages

2950-1600 BCE(?)

Olmec Long Count32 BCE

Arrhenius, 1896 (equilibrium)

Present day best estimate: 2.5-4.0°C with a best estimate of 3.0°C for 2100 from doubling CO2 from the IPCC 4th assessment, 2007

Svante Arrhenius (1859-1927)

What about future climate?Earth’s climate has changed frequently and

radically in the past

Could we be changing climate?

We are changing the atmosphere

The world has been warming

Sea level has been rising

6 m Sea Level Rise• more coastline than California!• more susceptible to sea level rise than all but 2 other states

Chesapeake Bay and Climate Change

Climate Modeling

Future climate depends on us.

Emissions

Figure TS.5

Projections of Future Climate

2090-2099

Global Precipitation Projections

Virginia’s Temperate Climate

Virginia Long-Term Average Temperature and Precipitation (1895-1998)

Month Maximum °F Minimum °F Average °F Precipitation (Inches)

Jan 45.8 26.0 35.9 3.13

Feb 47.7 26.7 37.2 3.08

Mar 56.9 34.1 45.5 3.86

Apr 67.1 42.7 54.9 3.29

May 75.8 52.2 64.0 3.99

Jun 82.9 60.2 71.5 3.69

Jul 86.1 64.3 75.2 4.31

Aug 84.6 63.2 73.9 4.14

Sep 79.2 57.0 68.1 3.50

Oct 69.2 45.0 57.1 3.36

Nov 57.8 35.4 46.6 3.21

Dec 47.8 28.0 37.9 3.18

Annual 66.7 44.6 55.7 42.70

Virginia ClimateBIG factors in VA Climate:

Atlantic Ocean and its warm Gulf Streamthe Blue Ridge and Appalachian mountain systems

Cold air from North, Warm from the south clash over Virginia

In the southern warmth in summer, northern cold in winter

A shift in that pattern means a shift in climate

Virginia Climate5 Regions:

Tidewater, Piedmont, Northern Virginia, Western Mountain and Southwestern Mountain

Highest temperature: 110° F. in Balcony Falls in Rockbridge County on July 15, 1954;

Lowest is -30° F on January 21, 1985, at the Mountain Lake Biological Station near Blacksburg

Greatest snowfall during a single storm: Big Meadows, SNP, 48” fell January 6-7, 1996.

Most snow to fall in a month: Warrenton in February 1899, 54”.

Mid-Latitude StormsFueled by temperature contrasts

Track west to east across N. America

Near the Atlantic coast, they move NortheastDue to contrasting land (cold) Gulf Stream (warm)

temperatures

Pulls in cold air from NW, warm moist air from E

Produces impressive storms!

VA typically a little too far south for the truly mean stuff (e.g. Nova Scotia)

Tropical stormsFueled by warm, moist tropical airmasses, which

come from warm ocean waters

Move from the Gulf or the Atlantic up the Eastern Seaboard

Get their knees chopped out from under them by the land

Interact in nasty ways with mountains!!!Lots of wind, rain, landslides, flooding, etc.

September VA can see 10-40% of its rainfall from tropical systems

Rain shadowsWhen winds are from the west:

New River and Shenandoah River are in the Rain shadow of the Appalachians

When winds are from the east:New River and Shenandoah River are in the Rain

shadow of the Appalachians

These valleys are drier than the rest of the state

ThunderstormsCan occur in any month of the year (think

“Tidewater”)

Are most frequent in the late afternoon (~4:30 PM)

Most frequent in southern VirginiaEspecially in the SW corner of the stateLeast frequent in N. Virginia

Current distribution of major forest types in the Mid-Atlantic Region (McKenney-Easterling et al. 2004).

Predicted dominant forest type distribution for GFDL, Hadley, and UKMO 2 X CO2

equilibrium scenarios (McKenney-Easterlinget al. 2004).

“Take-home” IdeasOur rock has a nice climate because of a happy

combination of sun, orbit, rotation, water, land and above all our atmosphere.

Virginia happily lies in the temperate zone

Weather derives from heating-driven turbulence on many scales

Weather forecasts are good and getting better

Our atmosphere is changing; our climate is changing with it; and it’s because of us. There’s really no serious doubt about this.

Virginia faces a warmer – maybe 6 °F – and somewhat wetter (0-10%?) future

What can I do?“Citizen Science”

Bud BurstTrack plant phenophase in your areahttp://www.windows.ucar.edu/citizen_science/

budburst/

Global Invasions Network (invasives are first in!)Garlic Mustard Surveyhttp://invasionsrcn.org/portal

No, really, what can I do?Can choose to get 100% of energy from wind

Can buy an electric vehicle

Can use less

Thank You!

Radiative BalanceThe atmosphere warms from the ground up

The sun’s warmth comes in at or near the visible part of the spectrum (aka “shortwave”) and heats the groundThe atmosphere is transparent to visible light

The ground radiates energy back into spaceThe atmosphere is nowhere near as transparent to

infrared light (aka “longwave”), so the atmosphere behaves like a see-thru blanket

Weather systems and ocean currents move energy, but in the end, something has to get warmer in order to release this excess energy back into space

Note: clouds, particles, etc., make this more complex

Blackbody RadiationEverything emits infrared (aka “longwave”) light

You, me, toasters, trees, squirrels, ice, everything

This goes according to the blackbody radiation law:Power = T4 (watts/square meter)

If we have:more energy being trapped and the only way to get rid if it is through blackbody

radiation, thenthe temperature must increase

Scenarios

Glacier melt?Certainly an issue

Probably will accelerate sea level rise

NOT in IPCC 2007 (missed cutoff)

Not as large as thought in 2005 (fast year for Greenland’s glaciers)

Stay tuned…

North American Projections

Structure of the Atmosphere

•Almost ¾ of the atmosphere is in the troposphere, in which all our weather occurs.•Temperature normally decreases with height by about 3.6°F per 1000 ft in the troposphere.•But dry air moved up or down changes temperature at about 5½°F per 1000 ft.•Jet aircraft fly near the tropopause, where temperatures are near -70°F.

How do we get ice ages?Early-mid 1800s: Idea of an ice age proposed, no

explanation for how

1842, Frenchman Joseph Alphonse Adhémar suggested that the varying lengths of winter and summer, an effect of the precession, causes ice to accumulate in the hemisphere with the longer winter.

Scotsman James Croll combined the eccentricity of the orbit and the precession and in the 1860s and 1870s presented his ideas on the effects of the cycles and how they might influence climate, especially the colder winters when they correspond with the aphelion, when Earth is farthest from the Sun

How do we get ice ages?Milankovitch gets most of the credit for relating

the cycles to ice ages because he incorporated all of the pertinent cycles, dealt with them in much greater mathematical precision and showed much more thoroughly how they affect climate.

Often, these cycles are called Milankovitch-Croll cycles

What about future climate change?

Orbital changes occur over thousands of years, and the climate system may also take thousands of years to respond to orbital forcing.

Theory suggests that the primary driver of ice ages is the total summer radiation received in northern latitude zones where major ice sheets have formed in the past, near 65 degrees north.

Past ice ages correlate well to 65N summer insolation (Imbrie 1982).

Astronomical calculations show that 65N summer insolation should increase gradually over the next 25,000 years

No 65N summer insolation declines sufficient to cause an ice age are expected in the next 50,000 - 100,000 years ( Hollan 2000, Berger 2002).