GLOBAL WARMING & CLIMATE SCIENCE JOOP VAREKAMP, E&ES

Structure of this presentation 1. Global warming-real or not? 2. Climate science, models and predictions the zero dimensional approach 3. Unexpected events

Is there evidence for Modern Global Warming? A. Instrumental records B. ‘Proxy’ records from the recent past C. Current Environmental Change (glaciers,floral/faunal shifts) How does MGW fit into the climate history of the recent geological past?

Source: OSTP

Source: IPCC TAR 2001 Variations of the Earth’s Surface Temperature* *relative to average

Superposed on gradual climate change, there is evidence for very sudden climate change from the record of the past

U.S. Temperature Trends: 1901 to 1998 Red circles = warming; Blue circles = cooling All stations/trends displayed regardless of statistical significance. Source: National Climatic Data Center/NESDIS/NOAA Crawford Ranch

Snow cover and ice extent have decreased

Crumbling of the Killimanjaro summit glacier - an effect of global warming

Collapse of the Larsen Ice Shelf near Antarctica - a piece of ice the size of Rhode Island came adrift

Melting of the Arctic and Antarctic Ice Caps

Global warming (temperature increase) Effects of global warming on water cycle Speeds up global water cycle More extreme weather events Droughts Droughts Storms Storms Floods Floods

Increase in catastrophic flood events

Increase in frequency and intensity of droughts Source: OSTP

Extreme Precipitation Events in the U.S. Source: Karl, et.al

So these are the data: There is global warming, there are more extreme events, ice is melting, glaciers are retreating, rainfall patterns are changing, plants and animal species are “moving”, sea level is rising. The real BIG question is: Natural Variability or the “Human Hand”?

The main “Radiation Law is Planck’s Law. Boltzman’s Law is the ‘integrated version’ of PL

The Human Hand?!

GLOBAL WARMING IS LIKELY RELATED TO THE GREENHOUSE EFFECT - HOW DOES THAT WORK?

FIRST WE SHOULD LOOK AT THE BASICS OF CLIMATE SCIENCE

Principle of Radiative Balance: The solid earth + atmosphere receive heat from the sun BUT also radiate the same amount of heat back into space

Principles of terrestrial climate: Incoming solar radiation equals outgoing terrestrial radiation R sun = R terr The magnitude of R terr depends on T s (apply Boltzman Law). Part of the outgoing terrestrial radiation is blocked by ‘greenhouse gases’, and the earth warms up a bit to restore the radiative equilibrium

Illumination of the earth by the sun: 1. More heat received at the equator than at the poles 2. Solid earth receives more heat by radiation than it radiates back RESULT: CONVECTIVE HEAT TRANSPORT FROM EQUATOR TO POLES THROUGH AIR AND OCEANS

The earth radiates long wavelength EMR which is absorbed by molecules with an uneven # of atoms, such as H 2 O, CO 2, CH 4, CFC’s O 3 (the “greenhouse” gases)

THE GREENHOUSE EFFECT THE SUN EMITS SHORT WAVELENGTH RADIATION (‘VISIBLE LIGHT’) WHICH PENETRATES THROUGH THE ATMOSPHERE AND HEATS THE SOLID EARTH. THE SOLID EARTH EMITS LONG WAVE LENGTH RADIATION (‘INFRA RED’) WHICH IS ABSORBED ‘ON ITS WAY OUT’ BY THE GREENHOUSE GASES. A THERMAL BLANKET IS THE RESULT

THE TRACE GASES (H 2 O, CO 2, CH 4, N 2 O, O 3 ) SERVE AS GREENHOUSE GASES AND KEEP THE EARTH LIVABLE

IF THE GREENHOUSE EFFECT IS CHANGING: CAN WE DOCUMENT CHANGES IN THE CHEMICAL COMPOSITION OF THE ATMOSPHERE? COULD THESE BE ANTHROPOGENIC? IS THEIR MAGNITUDE ENOUGH TO EXPLAIN MODERN GLOBAL WARMING?

Burning of fossil fuels Source: OSTP

Deforestation

Indicators of the Human Influence on the Atmosphere during the Industrial Era Source: IPCC TAR 2001

Source: OSTP

CARBON RESIDES IN AND MOVES BETWEEN DIFFERENT RESERVOIRS SUCH AS THE ATMOSPHERE, THE PLANT AND ANIMAL WORLD (BIOSPHERE), DISSOLVED IN THE OCEAN AND IN SOILS. THE CARBON MOVEMENTS BETWEEN THESE RESERVOIRS IS CALLED THE CARBON CYCLE

ANTHROPOGENIC CARBON FLUXES IN THE 1990s: FOSSIL FUEL BURNING: 6 BILLION TONS CARBON/YEAR DEFORESTATION: 1.1 BILLION TONS CARBON/YEAR TOTAL: 7.1 BILLION TONS CARBON/YEAR WHERE IS ALL THAT CO 2 GOING??

How do we model future atmospheric CO 2 concentrations? Apply a carbon cycle model to a range of future FFF scenarios Use ‘economic scenarios’ that depend strongly on 1.Population growth rates 2.Economic development 3.Switch to alternative energy technologies 4.Sharing of technology with the developing world

Carbon cycle model from E&ES 132/359 at Wesleyan University Symbols: M x = mass of carbon K x = rate constant FFF = Fossil Fuel Flux of Carbon Feedbacks: Bf = Bioforcing factor; depends on CO 2 (atm) K 4 = f(temperature)

CO 2 and SO 2 in the 21 st Century Source: IPCC TAR 2001

Clear correlation between atmospheric CO 2 and temperature over last 160,000 years Clear correlation between atmospheric CO 2 and temperature over last 160,000 years Current level of CO 2 is outside bounds of natural variability Current level of CO 2 is outside bounds of natural variability Rate of change of CO 2 is also unprecedentedRate of change of CO 2 is also unprecedented Source: OSTP

If nothing is done to slow greenhouse gas emissions... If nothing is done to slow greenhouse gas emissions... CO 2 concentrations will likely be more than 700 ppm by 2100 CO 2 concentrations will likely be more than 700 ppm by 2100 THIS IS WELL OUTSIDE THE THIS IS WELL OUTSIDE THE ‘NATURAL RANGE’ OF THE ‘NATURAL RANGE’ OF THE LAST 200,000 YEARS LAST 200,000 YEARS 2100 Source: OSTP

To go from atmospheric CO 2 concentration change to climate change, we need to know the climate sensitivity parameter,. The common approach is:  T s =  F  or  F/  T s = 1/ where  F is the ‘radiative forcing’ caused by the increased CO 2 concentration. The value of  F can be calculated from the increase in CO 2 concentration using the deBeers law.  T s is the change in the surface temperature of the earth We can solve for by taking the first derivative of Boltzman’s Law F =  T s 4 or dF/dT s = 4F/T s leading to a value of 0.3 K/Wm -2. This approach is the most fundamental response function and uses zero climate feedbacks! Most climate modellers use 0.5 K/Wm -2, incorporating various positive and negative feedbacks.

Global average temperature is projected to increase by 1.5 to 5.8 °C from 1990 to 2100 Projected temperature increases are greater than those in the SAR (1.0 to 3.5 °C) Projected rate of warming is unprecedented for last 10,000 years Temperature Projections Source: IPCC TAR 2001

CONCLUSIONS: Global warming is here! Its effects have been documented extensively worldwide The human hand is, according to many, very visible Projections for the future are riddled with uncertainties, but all show further warming Largest source of uncertainty are the economic scenarios.

A recent movie suggested that global warming may lead to the early arrival of the next Ice Age? or

Could these be related?

WHICH OF THESE SYMBOLS WILL BE THE STRONGER ONE??

CONCLUSIONS (2): Natural climate variability over the last 700,000 years is finely in tune with planetary motions-Ice ages do not occur at random! Superposed there are sudden climate changes (e.g., Younger Dryas) that have other origins (e.g., shut down of oceanic conveyor) As such, global warming can lead to sudden arrival of a new cold period (but over decades, not hours!)