Almost on a daily basis, we hear news or pieces on TV or on the radio about climate change. From the Bali talks, to the primary elections, to physical changes in the Arctic, the term climate change emerges constantly in our daily lives. The IPCC reports that "warming of the climate system is unequivocal", as we have available observations of increases in global average temperatures, the melting of snow and ice, and the rising of global average sea level.

Climate Change is caused by changing atmospheric conditions. Changes in the concentration of green house gases (GHG) and aerosols, as well as changes in plant cover and solar radiation alter the energy balance of the atmospheric system. The IPCC also shows that global GHG emissions due to human activities have grown since pre-industrial times, with an increase of 70% between 1970 and 2004.

Carbon dioxide (CO2) is the most important anthropogenic GHG. Its annual emissions grew by about 80% between 1970 and 2004. The long-term trend of declining CO2 emissions per unit of energy supplied reversed after 2000. Atmospheric concentrations of CO2 (379ppm) and CH4 (1774 ppb) in 2005 exceed by far the natural range over the last 650,000 years. Global increases in CO2 concentrations are due primarily to fossil fuel use, with land-use change providing another significant but smaller contribution. There is high agreement and much evidence that with current climate change mitigation policies and related sustainable development practices, global GHG emissions will continue to grow over the next few decades. (IPCC, Summary for Policy Makers, 4th Assessment Report, Synthesis Report).

Seen in a humanitarian and developmental sense, climate change is one of our most pressing issues, and its full impact might be detrimental to the efforts of eradicating poverty. The Human Development Report (HDR) of 2007-2008 states that "failure to respond to that challenge will stall and then reverse international efforts to reduce poverty. The poorest countries and most vulnerable citizens will suffer the earliest and most damaging setbacks, even though they have contributed least to the problem." In this sense, we can see the detrimental effects of climate change as a double injustice: the ones that did not contribute much are the ones that are going to pay for it the most.

Finally, and most importantly, the HDR formulates that climate change "in a divided but ecologically interdependent world, challenges all people to reflect upon how we manage the environment of the one thing that we share in common: planet Earth. It challenges us to reflect on social justice and human rights across countries and generations. It challenges political leaders and people in rich nations to acknowledge their historic responsibility for the problem, and to initiate deep and early cuts in greenhouse gas emissions. Above all, it challenges the entire human community to undertake prompt and strong collective action based on shared values and a shared vision."