How does burning coal contribute to both increasing and decreasing global temperature? What will ...

(Answer to question 1 )  Burning coal releases carbon dioxide, which is a greenhouse gas that causes global warming. However, coal also contains sulfur-bearing minerals that release sulfurous aerosols when burned. These sulfurous aerosols, released into the atmosphere, absorb incoming solar radiation, so this is a cooling effect.

(Answer to question 2 )  The carbon cycle describes a complex interconnection of processes that move carbon atoms within complex molecules from living tissues, to rocks, to water, and to the atmosphere. The organic carbon in all organisms originates as carbon dioxide in the atmosphere that is incorporated into plants by photosynthesis (and then into animals when they eat the plants). Therefore, photosynthesis removes carbon dioxide from the atmosphere. When organisms die, some of the carbon remains in soil or organic matter buried in sediment, but that part of the organic carbon that decays is converted back to carbon dioxide that can be released to the atmosphere. Not all of the carbon dioxide generated by decaying organic matter in the oceans returns directly to the atmosphere, however, because a lot of it dissolves in the ocean as carbon dioxide. This also means that carbon dioxide moves back and forth between the ocean and the atmosphere, which causes either increases or decreases in atmospheric CO2. Geologic processes also affect the carbon cycle, because carbon dioxide in the atmosphere mixes with water to form a weak acid that is consumed in weathering reactions that break down rocks. This means that atmospheric carbon dioxide concentrations decrease when rock weathering rates increase. Carbon-bearing molecules dissolved in water are also incorporated into carbonate minerals that precipitate to form rocks like limestone.

(Answer to question 3 )  Warm water is less dense than cold water and salty water is denser than fresh water. These effects on water density explain a conveyor-belt-like circulation pattern in the North Atlantic Ocean. Surface water currents moving northward from the equator are warm but are also saltier than normal because of excessive evaporation at tropical latitudes. The decrease in density related to the temperature change just slightly outweighs the density increase related to the salinity change; therefore, the water remains at or close to the surface as it moves northward. At higher latitudes, this warm, salty water encounters colder polar air. Heat is radiated from the water into the air, which warms it. This transfer of heat from the ocean to the atmosphere explains the moderate winter temperatures in northwestern Europe, which lacks the extreme cold and heavy snowfall experienced at similar latitudes in Asia and North America. However, when the heat radiates from the ocean, the temperature decreases so that now the water in the North Atlantic Ocean is both cold and salty; both factors increase the water density. The dense water sinks and more warm, salty water moves up from the south to replace it. The sinking of cold, salty water is like the downward moving return loop on a conveyor belt and it draws more warm water northward.

(Answer to question 4 )  El Nio and La Nia describe contrasting conditions of surface-water temperature off the western coast of South America. During an El Nio, the water is warmer than normal and during La Nia the water is cooler than normal. These two departures from average conditions result from interactions between wind and ocean circulation. In normal years, easterly trade winds cause ocean currents in the Pacific Ocean that move away from South America, allowing cooler water to rise from depth to the surface. During El Nio years the trade winds are weak and the westward flowing currents cease. This means that tropically heated water remains in the eastern Pacific Ocean and the colder water doesn't upwell from depth. With La Nia conditions, the trade winds are exceptionally strong, and move the upwelling water far across the Pacific Ocean.

(Answer to question 5 )  Computer models can be used to calculate global temperatures based on changes in Earth's energy budget that can be related to both natural processes and human activities. The temperatures calculated from the computer models can then be compared to the actual measured temperatures. If only natural processes are used in the computer models, then the calculated and measured temperatures are similar prior to about 1970. After 1970, however, calculated and measured temperatures match only by including warming attributed to human activities.

(Answer to question 6 )  To estimate future temperature changes, scientists primarily examine different scenarios for fossil-fuel consumption based on projections of population growth (energy needs grow as population grows) and various expectations for conserving fossil fuels or replacing them with energy sources that do not emit greenhouse gases. These scenarios for fossil-fuel consumption are then used to estimate the changing concentration of greenhouse gases in the atmosphere, which is the most important factor for predicting future temperature change.

Don't forget to rate the answer too