CLIMATE CHANGE AT GLOBAL LEVEL

1. CLIMATE CHANGE AT GLOBAL LEVEL

2. INDEX • The first studies: climatechanges • Albedo • Volcanoes and volcaniceruptions • Oceancurrents and C O2 • Change in temperature and greenhousegasesovertime • Permafrost • Water vapour and clouds • Solarvariation • Displacementof the tropics

3. The first studies:the climate change It is arguedthat the current change of the climate is provocated by carelessactions of people. The Earthhas the ability to react to this change but in a very long time so, forthisreason, people risk to self-destruct. Scientists believethat: • The average temperature of Earth’s atmosphere is increasing; • The concentration of greenhousegases in the atmosphere is increasing; • There is a correlationbetween the increase in temperature and the increase in the concentrationof green house gasesin the atmosphere; • The increasedconcentrationof green house gasesin the atmosphere is due to anthropogenicemissions.

4. Scientists suppose thatthere are effects due to global warming : • Reducing volume of glaciers: since the end of the littleiceage, glaciers of mountain ranges are in sharpdeclineover the wholeearth. • Oceans are warmer and acids : the oceansurface is 30% more acidicthanitwas in 1800, and 50% of this change has come from the increament of CO2 in the atmosphere, endangering coral reefs and various species of plankton that form the base of the food chain of the sea. • Average temperature differencebetweenday and night is easing: another change concerns the thermal shock thatoccursbetween the day and the night, and thatturns out to bestrongerthan in previousyears.

5. Animals are shiftingtheir habitat poleward: climatechangemeansalsochanges in the life ofanimalswhichmake a considerableefforttoadapt, hence the pole shift. • Plantsbloomdays or weeksearlierthan in the past: the percentage of endangeredspeciescompared to thoseanalyzed is 69%, whilecompared to the knownones is 2%.

6. Factorsthataffect the climate The climatechanges and thisdepends on variousfactors: • the albedo; • volcanoes and volcaniceruptions; • the absorptionof Co2 and oceanscurrents; • changesof the temperature and greenhousesgasesovertime; • the permafrost; • water vapor and clouds; • the variationofsolaractivity; • the displacement of the tropics.

7. Albedo The albedo is the ratiobetween the amountofsolarenergyreflectedfrom the Earth-atmosphere system and the total energycominginto the system. The albedo of the Earth-atmosphereis 0,35.

8. A completely white surface has an albedo of 1, because it reflects all the light. A completely black surface has an albedo of 0 because it absorbs solar rays. Therefore a surface without snow or ice absorbs more radiation.

9. Consequencesof the albedo One of the more evidentconsequences is the melting of the ice, that, being white, reflects a very effective radiation, while the water and the soil , being darker, reflects less. The more ice melts because of the increment in temperature, the more soil and water become widespread, and the greater the absorption of heat by the planet is.

10. Volcanos and volcanic eruptions A volcano is a geologic, complicated rocky structure, which is generated in the Earth’s crust by the ascent of the magma formed below or in the Earth’s crust. A volcanic eruption is the leakage of magma and other gaseous materials in the Earth’s surface from the mantle or the crust. Typically a volcanic eruption happens either in the main crater of a volcano or in the minor craters of the volcano. The classification is based on the characteristics of magma and on the type of eruption.

11. Consequences of the vulcanic activities • Volcanic eruptions are capable of triggering climate change in a short time with an efficiency that is unmatched in nature. • In a few months, the atmospheric temperature of the Earth can drop, causing droughts, floods and cold weather.

12. C O2 ABSORPTION AND OCEANIC CURRENTS Not all of the carbon dioxide we produce stays in the atmosphere, oceans absorb 1/3 and ¼ of C O2every year. This gas dissolves in salty water, creating carbonic acid . Since the concentration of atmospheric C O2, keeps increasing, oceans absorb more and more C O2, thus producing more and more carbonic acid. This acid is changing the chemical balance of the oceans: the process is known as “ocean acidification”. Thermohaline circulation: this is the global oceanic circulation due to the variation of density of the water masses. A oceanic current is a mass of sea water in movement with respect to the surrounding water and from which it is different in density, salinity, temperature or colour.

13. Trends in temperature and green house gases during time The greenhouse gases present in the atmosphere are about 30 and they can capture heat. The water vapour is the most efficient gas in the control of the air temperature of the Earth’s surface. Greenhouse gases are necessary to trap the energy irradiated by surface of the Earth which, otherwise, would be extremely cold. This process limits the flux of energy going outside.

14. The results show that the Earth's temperature will increase as the greenhouse gases increase. The gas considered as the most important for the green house effect is the CO2 issued into the atmosphere from the consumption of fossil fuels for human activities. In addition to carbon dioxide, there are other greenhouse gases whose quantity is increasing.

15. The datas of the Earth’s athmosphere in the past were obtained from the growth of rings of the trees or by the relationships between the isotopes of various elements in the glaciers of Antarctica and Greenland, and in the corals or in lake sediments. From all these data we obtain the average global temperature in the past, and these data are essential to defeat the "global warming". The reconstruction of past temperatures based on indirect data is a very difficult path.

16. In areas in high latitudes, where temperatures are very low, the soil is called permafrost, namely "permanently frozen." It is divided into several layers that can be up to a hundred meter deep. Permafrost was formed by the last glaciation and permafrost is divided into: saturated and supersaturated soil. Due to the increment in temperature, permafrost is starting to melt permanently. Permafrost

17. Some plants can live into the melting and when they die they don’t decompose butwith permafrost remainintactforthousands of years and thishasmade the permafrost a big carbonsink. With the increaseof temperature, however, the planetwarms and the permafrost may start toemitgreenhousegasesthat can amplify the effectsof global warming.

18. The cloudsoccupyabouthalf the atmosphericsurface and thishave a significanteffect on the budget radioactiveterrestrialbased on theirthickness. According to the Iris effect a warmerEarthwould produce more water vapor in order to protect the Earth from the sun's rayslimiting warming. Butaccording to anotherhypothesis the cloudsshouldtrapheat and strengthen the heating. But the cloud cover increase the green effect. Clouds

19. The sun, our star, givesusheat, light and energy. Itis a greatnuclearpower and hydrogenpresentssuddenchanges in itsactivephase. In the pastwehadseveralepochalclimatechangegoingfrom a tropicalclimate in the Jurassiceratoglaciation in the QuaternaryIceAge. Thisiscausedbyanimportantchange in energy production of the Sun. Variationof the sunactivity

20. According to a survey the displacement of the tropicscoincideswith the rise in temperature of 0.8 degrees Celsius. Because the masses of warmtropicalair-moveaway from the equator. The Hadleycells are a type of convectivecirculation and precipitationdetermineboth the equatorial and subtropicaldrought. The displacement of the tropics

21. The end