Students:

Farcas Alex

Moldovan Maria

Bolba Filip

Danci Cornel

Teacher: Gutu Lucia

• Climate is long-term effect of solar radiation on various surfaces and the atmosphere of the Earth, which is manifested by changes in factors atmospheric while it rotates. Best be understood as the average annual temperature change combined with the average rainfall in a given geographical area.

• CLIMATE word comes from Greek, which means klima inclination sun. The climate is mainly influenced by solar radiation and its annual variations, of latitude, but also the complex structure of the atmosphere, the altitude, the proximity to the ocean or sea, of forms of relief (especially mountains and hills). Climate has profound effects on all life forms on Earth, microorganisms, plants, insects, animals, birds and people. Human activity can affect climate by: - earth changes - cutting forests - draining lakes, swamps and marshes - industrial pollution.

Causes

• Factors that can shape climate are climate forcings. These include such processes as variations in solar radiation, deviations in the Earth's orbit, mountain-building and continental drift, and changes in greenhouse gas concentrations. There are a variety of climate change feedbacks that can either amplify or diminish the initial forcing. Some parts of the climate system, such as the oceans and ice caps, respond slowly in reaction to climate forcing because of their large mass. Therefore, the climate system can take centuries or longer to fully respond to new external forcings.

Plate tectonics

• Over the course of millions of years, the motion of tectonic plates reconfigures global land and ocean areas and generates topography. This can affect both global and local patterns of climate and atmosphere-ocean circulation

Solar output

• The sun is the predominant source for energy input to the Earth. Both long-and short-term variations in solar intensity are known to affect global climate.

Orbital variations

• Slight variations in Earth's orbit lead to changes in the seasonal distribution of sunlight reaching the Earth's surface and how it is distributed across the globe. There is very little change to the area-averaged annually averaged sunshine; but there can be strong changes in the geographical and seasonal distribution. The three types of orbital variations are variations in Earth's eccentricity, changes in the tilt angle of Earth's axis of rotation, and precession of Earth's axis. Combined together, these produce Milankovitch cycles which have a large impact on climate and are notable for their correlation to glacial and interglacial periods, their correlation with the advance and retreat of the Sahara, and for their appearance in the stratigraphic record.

• Human activity- The constant growth of the average temperature of the planet since the middle 20th century is caused by emissions of greenhouse gases caused by humans;- General warming observed in the atmosphere and the ocean, and reducing ice mass confirms that it is "extremely unlikely" that climate changes in the last 50 years have been caused only by natural factors;- "Past and future emissions of carbon dioxide will contribute to warming and increasing sea levels over the next planet a thousand years", due to persistence in the atmosphere of greenhouse gases

• Greenhouse gases are gases in an atmosphere that absorb and emit radiation within the thermal infrared range. This process is the fundamental cause of the greenhouse effect. The main greenhouse gases in the Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone. In our solar system, the atmospheres of Venus, Mars and Titan also contain gases that cause greenhouse effects. Greenhouse gases greatly affect the temperature of the Earth; without them, Earth’s surface would be on average about 33 °C (59 °F) colder than at present.

• The contribution to the greenhouse effect by a gas is affected by both the characteristics of the gas and its abundance. For example, on a molecule-for-molecule basis methane is about eight times stronger greenhouse gas than carbon dioxide, but it is present in much smaller concentrations so that its total contribution is smaller. When these gases are ranked by their contribution to the greenhouse effect, the most important are: • water vapor, which contributes 36–72% • carbon dioxide, which contributes 9–26% • methane, which contributes 4–9% • ozone, which contributes 3–7%

• It is not possible to state that a certain gas causes an exact percentage of the greenhouse effect. This is because some of the gases absorb and emit radiation at the same frequencies as others, so that the total greenhouse effect is not simply the sum of the influence of each gas. The higher ends of the ranges quoted are for each gas alone; the lower ends account for overlaps with the other gases. The major non-gas contributor to the Earth’s greenhouse effect, clouds, also absorb and emit infrared radiation and thus have an effect on radiative properties of the greenhouse gases.

• Increasing atmospheric carbon dioxide levels as measured in the atmosphere and reflected in ice cores. Bottom: The amount of net carbon increase in the atmosphere, compared to carbon emissions from burning fossil fuel. Aside from purely human-produced synthetic halocarbons, most greenhouse gases have both natural and human-caused sources. During the pre-industrial Holocene, concentrations of existing gases were roughly constant. In the industrial era, human activities have added greenhouse gases to the atmosphere, mainly through the burning of fossil fuels and clearing of forests.

• As a result of this balance, the atmospheric concentration of carbon dioxide remained between 260 and 280 parts per million for the 10,000 years between the end of the last glacial maximum and the start of the industrial era. It is likely that anthropogenic warming, such as that due to elevated greenhouse gas levels, has had a discernible influence on many physical and biological systems. Warming is projected to affect various issues such as freshwater resources, industry, food and health.

• The Greenland and Antarctic ice sheets have decreased in mass. Data from NASA's Gravity Recovery and Climate Experiment show Greenland lost 150 to 250 cubic kilometers (36 to 60 cubic miles) of ice per year between 2002 and 2006, while Antarctica lost about 152 cubic kilometers (36 cubic miles) of ice between 2002 and 2005

http://climate.nasa.gov/galleryLarge/ImageLarge-27.jpg

• EFFECTS- The most significant warming in the areas of land will be released before the water surface or at high latitudes, while in the southern Indian Ocean and in parts of the North Atlantic will be smaller effects;- Simulation exercises provide for a reduction of ice in the Arctic and Antarctica all climate scenarios, in some cases, the ice would disappear almost entirely in the Arctic Ocean in the second half of the 21st century;