The Earth’s climate is determined by a continuous flow of energy from the sun.

Thermal energy from the sun penetrates the Earth’s atmosphere and warms its surface. As the temperature of the surface rises, the Earth sends thermal energy back into the atmosphere in the form of infrared radiation. Part of this energy is absorbed by gases (called greenhouse gases), such as carbon dioxide, methane, nitrous oxide and water vapor, which trap it in and maintain the Earth’s average temperature at about 15 °C, the required temperature level for sustaining life for humans, plants and animals. Without these gases, the Earth’s temperature would fall as low as -18 °C, freezing most life forms. 

Carbon dioxide (CO₂) is the most important of the gases that maintain the appropriate temperature level on Earth.
CO₂ emission and absorption processes occur in nature forming the gas’s natural cycle. These processes maintain a balanced CO₂ concentration in the atmosphere.
 
 Through volcanic eruptions, plant decay and animal respiration, CO₂ is released into the atmosphere and is then absorbed once again through photosynthesis and water dissolution (e.g., in the ocean).

Nature has provided for an almost perfect balance between the amounts of emitted and absorbed CO₂. However, even small changes brought on by human activities can affect this fragile balance.

Climate change is caused by the excessive use of mineral resources, such as carbon, lignite, oil and natural gas, whose burning releases vast amounts of CO₂ into the atmosphere. Therefore, the blanket of greenhouse gases that cover the Earth traps more and more energy, which in turn increases the planet’s average temperature.

During the past 150 years, human intervention in the CO₂ natural cycle has been decisive. The irrational burning of fossil fuels and livestock breeding activities that contribute to methane emissions, combined with the clearing of forests, which absorb greenhouse gases, have irreparably disturbed the balance of the CO₂ cycle.

The great atmospheric concentration of CO₂ has contributed to the increase of the planet’s temperature—an increase occurring faster than any other natural process. As a result, natural systems are unable to adapt to the new conditions.

It is clear that the rise in global temperature does not mean a warmer climate for everyone in every part of the world. As the planet heats up, the climate system is altered, and extreme and unpredictable weather phenomena become increasingly frequent. As a result, some areas will be warmer, and others will be colder. Similarly, humidity levels will be affected as well, resulting sometimes in drought and others in excessive rainfall.

Limiting the increase in temperature to 2 °C has been recognized by the scientific community and the European Union as a necessary condition to prevent the worst impacts of climate change.

Severe consequences on human populations and ecosystems—such as the melting of glaciers in the Arctic—are already being observed even with the current 0.8 °C increase in relation to pre-industrial levels. Said consequences could trigger positive feedbacks, which will further increase temperature and lead to more devastating consequences on the planet’s ecosystems.

• The Fourth Assessment Report (AR4) of the Intergovernmental Panel on Climate Change (IPCC) further predicts that:
• within coming decades, water supplies stored in glaciers and snow cover will be reduced, resulting in a lack of water for more than 1 billion people; 
• 20–30% of the planet’s living organisms will face an increased risk of extinction, should the rise of the average global temperature exceed 1.5–2.5 °C;
• in lower geographical latitudes and mostly in dry and tropical areas, even small rises of 1–2 °C will increase the risk of starvation;
• after 2080, millions of people will be affected by floods in their residence or business due to sea-level rise. Densely populated areas and areas in low altitudes with limited adaptation capabilities are particularly at risk.

Greece’s wealth is inextricably linked to its climate. The warm and dry climate of the Greek summer combined with thousands of kilometers of coastline attracts tourists from around the world. Warm summers combined with mild humid winters encourage the development of agriculture as an inseparable part of the Greek economy. Under the same conditions, thousands of hectares of forest cover host a wide range of biodiversity. Today, this natural wealth is under great pressure due to population growth and uncontrolled development. Global warming will bring on even greater pressures for our country. A UN study has shown that Greece and the entire Mediterranean basin are among the 18 hot-spots of the planet, which will be facing the gravest problems caused by the intensified climate change.

A scientific study by WWF Greece and the National Observatory of Athens entitled The future of Greece attempts to predict climate conditions in Greece for the period 2020–2050, that is, for the imminent future.

According to the study’s findings, the already existing discomfort of urban populations will be aggravated. Inhabitants of cities such as Thessaloniki, Patra, Lamia and Larisa will be submitted to 20 more days of heatwaves. At the same time, in Lamia, Larisa, Volos, Thessaloniki and Athens, total precipitation will be reduced, but extreme rainfall is expected to increase by 10–20%. In other words, the risk of flood and the risk of fire spreading to suburban forests appear to be increased.

Greek tourist destinations will also be significantly affected. The tourist regions that were part of the study will have from 5 to 15 more heatwave days, while the number of nights with temperatures above 20 °C will also increase, mainly in island areas, such as Rhodes and Chania.

The ten larger agricultural regions of the country will also receive a lot of pressure due to climate change. Heatwave days and continuous dry days will increase, and winter rainfalls will decrease. As a result, the risk of wildfire will increase significantly. In Evia, for example, 25 more dry days are expected, and Serres and Larisa will see 20 more heatwave days. In Heraklion and Pella, winter rainfalls will decrease by 15%. There is also increased risk of desertification and reduced water availability.

Climate change will also put significant pressure on National Parks, considering that high wildfire risk days are expected to increase in all of the country’s Parks.

Lastly, in a related report published in 2011, the Bank of Greece underlines that the economic cost of climate change is very high for our country: in the worst case scenario, the costs for the Greek economy by 2100 add up to 701 billion euros, an amount that is more than twice our national debt in 2009. The report’s editors note that adopting climate protection policies is the most economical option. If Greece drastically reduces emissions in line with corresponding global efforts, the overall costs will be reduced by €265 billion, totaling €436 billion.