Climate change is now acknowledged as the biggest challenge facing our global environment and the human species today. It can be defined as a change in global and regional patterns over time. Through daily efforts to reduce their environmental impacts, participants in the Green-Schools programme can lead Ireland's battle against climate change. Indeed many of the measures being undertaken under the themes of Litter and Waste, Water, Energy, Travel, Biodiversity and Citizenship are already having a positive impact in this respect.