Global Warming

Causes

Including:Greenhouse EffectsSolar VariationsFeedbacksGlobal Dimming

Mostly from human activity

Causes

The world's leading climate scientists said global warming has begun, is very likely caused by man, and will be unstoppable for centuries. The phrase very likely translates to a more than 90 percent certainty that global warming is caused by man's burning of fossil fuels. That was the strongest conclusion to date, making it nearly impossible to say natural forces are to blame.

The scientists said global warming's connection varies with storms in different parts of the world, but that the storms that strike the Americas are global warming-influenced.

- The New York Times Report, February 2007

Causes ~ Greenhouse Effects

Emission of infrared radiation.

Greenhouse – house heated up by solar radiations. For planting plants, warms air near ground, trapping air from rising and flowing away.

Causes ~ Greenhouse Effects

Discovered by Joseph Fourier in 1824.

Planetary energy balance. Planets lose energy by chaleur obscure.

Balance reached between heat gain and heat loss.

Later, known as Stefan–Boltzmann law (50 years later).

Causes ~ Greenhouse Effects

Later, described qualitatively by Svante Arrhenius.

First man who speculated changes CO2 in the atmosphere could substantially alter the surface temperature through the greenhouse effect. ["On the Influence of Carbonic Acid in the Air Upon the Temperature of the Ground", Philosophical Magazine 1896(41): 237-76]

Formulated Arrhenius' greenhouse law

if the quantity of carbonic acid increases in geometric progression, the augmentation of the temperature will increase nearly in arithmetic progression.

Causes ~ Greenhouse Effects

Intergovernmental Panel on Climate Change Fourth Assessment Report. (Chapter 1: Historical overview of climate change science) said that average earth surface temperature is 15 °C (33 °C warmer without Greenhouse Effects)

Increasing Greenhouse

Gasses causes

Global Warming.

Causes ~ Greenhouse Effects

Greenhouse gasses – components of atmosphere that contribute to greenhouses effects.

include in the order of relative abundance water vapour, carbon dioxide, methane, nitrous oxide, and ozone.

Causes ~ Greenhouse Effects

Causes ~ Greenhouse Effects

Measurements of Pollution in the Troposphere

MOPITT carbon monoxide over India

MOPITT 2000 global carbon monoxide

Causes ~ Greenhouse Effects

Increases in carbon dioxide cause the earth to get warmer

Greenhouse gases in the atmosphere absorb heat radiating from the earth.

This trapped heat increases the evaporation of water from the oceans into the air to cause a greater increase in warming of the atmosphere. CO2 has a forcing effect on climate.

The combined effect of water vapor, carbon dioxide and methane controls the temperature of the earth.

Causes ~ Greenhouse Effects

Causes ~ Greenhouse Effects

CO2 level is increasing in the atmosphere

CO2 is produced by burning woods etc

Current level 280ppm to 370ppm

This increase → increase heat absorb by the earth

Causes ~ Greenhouse Effects

IPCC predicts atmospheric concentration of CO2: 541ppm to 940 in 2100.

Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.

Causes ~ Greenhouse Effects

Causes ~ Solar Variation

Few paper claim that Sun’s also contribute to increase global temperature.

About 40% to 50% in 1900 - 2000 and 25% to 35% in 1980 – 2000.

Cooling effect from volcano dusk and sulfate aerosols .

Causes ~ Solar Variation

Galactic Cosmic Rays Magnetic activity of the sun is

a crucial factor which deflects cosmic rays that may influence the generation of cloud condensation nuclei and thereby affect the climate.

Warming most of stratosphere (greenhouse gas theory predicts cooling here)

Reduction of stratospheric ozone has cooling influence

Causes ~ Solar Variation

Solar variation combined with changes in volcanic activity.

Pre-industrial times to 1950: warming effects

Then, it’ll be cooling effect Researchers claim that no

net increase of solar brightness over the last thousand years.

BUT, solar cycles led to a small increase of 0.07% in brightness over the last thirty years.

Causes ~ Solar Variation

Sami Solanki, the director of the Max Planck Institute for Solar System Research in Katlenburg-Lindau, Germany said:

“The sun has been at its strongest over the past 60 years and may now be affecting global temperatures... the brighter sun and higher levels of so-called "greenhouse gases" both contributed to the change in the Earth's temperature, but it was impossible to say which had the greater impact”

Solanki agrees with the scientific consensus that the marked upswing in temperatures since about 1980 is attributable to human activity.

"Just how large this role [of solar variation] is, must still be investigated, since, according to our latest knowledge on the variations of the solar magnetic field, the significant increase in the Earth’s temperature since 1980 is indeed to be ascribed to the greenhouse effect caused by carbon dioxide."

Stott's 2003 work mentioned in the model section above largely revised his assessment, and found a significant solar contribution to recent warming, although still smaller (between 16 and 36%) than that of the greenhouse gases.

Causes ~ Feedback

Methane release from melting permafrost peat bogs

Western Siberia – world largest peat bogs.

Formed last 11000 years ago (end of Ice Age)

Expected to release 70,000 tonnes methane in next few decades

Causes ~ Feedback

Methane release from hydrates

Methane clathrate water ice which contains a large amount of methane.

Can be found on ocean floor.

The sudden release of Methane hydrates could cause runaway greenhouse effects.

Causes ~ Feedback

According to the clathrate gun hypothesis a runaway greenhouse effect could be caused by liberation of methane gas from hydrates by global warming if there are sufficient hydrates close to unstable conditions.

Melting permafrost peat bogs and methane hydrate.

Methane being 21-times more potent a greenhouse gas than carbon dioxide

Causes ~ Feedback

Carbon cycle feedbacks. Cause loss of carbon from

terrestrial ecosystems, leading to an increase of atmospheric CO2 levels.

One model in particular (HadCM3) indicates a secondary carbon cycle feedback due to the loss of much of the Amazon rainforest in response to significantly reduced precipitation over tropical South America.

Researchers suggest any such feedback would accelerate global warming.

Causes ~ Feedback

Forest Fires Releasing carbon in the

atmosphere than the carbon cycle can naturally re-absorb.

Rising global temperature might cause forest fires to occur on larger scale, and more regularly.

Causes ~ Feedback

Retreat of sea ice. The sea absorbs heat from

the sun, while the ice largely reflects the sun rays back to space.

Retreating sea ice will allow the sun to warm the now exposed sea water, contributing to further warming.

Think of Black Car heats up faster then White Car.

The trend for global sea ice, northern hemisphere and southern hemisphere combined is clearly a decline.

Causes ~ Global Dimming

Burning of fossil fuels is creating two effects: Greenhouse gases

that cause global warming

By-products which are pollutants that cause global dimming

Causes ~ Global Dimming

Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth's surface that was observed for several decades after the start of systematic measurements in 1950s.

Caused by an increase in particulates such as sulfur aerosols in the atmosphere due to human action.

4% reduction over the three decades from 1960–1990.

This trends is reversed from past decades.

Interfered with the hydrological cycle by reducing evaporation and may have caused droughts in some areas.

Cooling effect: Greenhouse effects

Causes ~ Global Dimming

Fossil fuel use, as well as producing greenhouse gases, creates other by-products.

These by-products: Pollutants.

These pollutants: change the properties of clouds.

Polluted air results in clouds with larger number of droplets than unpolluted clouds → clouds more reflective.

Causes ~ Global Dimming

Climatologists studies: reflection of heat made waters in the northern hemisphere cooler.

Resulting less rain in Northern Africas.

What came out of our exhaust pipes and power stations contributed to the deaths of a million people in Africa, and afflicted 50 million more with hunger and starvation.

The Asian monsoons bring rainfall to half the world’s population.

Causes ~ Global Dimming

After 911, all commercial flights were grounded for the next three days.

Which allows climate scientists to look at the effect on the climate when there were no contrails and no heat reflection.

Result: Temperature is up 1 degrees in three days.

Causes ~ Global Dimming

Currently, most climate change models predict a 5 degrees increase in temperature over the next century, which is already considered extremely grave.

However, global dimming has led to an underestimation of the power of global warming.

Global dimming can be dealt with by cleaning up emissions.

Causes ~ Global Dimming

Europe 2003. various measures have been

taken to clean up the emissions without reducing the greenhouse gas emissions in parallel.

Effects: This may have already

lessened the severity of droughts and failed rains in the Sahel.

Contributed to European heat wave in 2003 that killed thousands in France, saw forest fires in Portugal, and caused many other problems throughout the continent.

Causes ~ Global Dimming

Addressing global dimming only would increase global warming more rapidly.

Irreversible damage would be only about 30 years away.

The melting of ice in Greenland. Drying tropical rain forests would

increase the risk of burning. Releasing more CO2.

These and other effects could combine to lead to an increase of 10 degrees centigrade in temperature over the next 100 years, not the standard 5 degrees which most models currently predict.

Causes ~ Global Dimming

Climatologists are stressing that the roots of both global dimming causing pollutants and global warming causing greenhouse gases have to be dealt with together and soon.

We are running out of time.