The combustion of fossil fuels for the purpose of energy generation is a major contributor to climate change. The burning of coal, oil and gas generates carbon dioxide - one of the major greenhouse gases thought to cause global warming.
In order to tackle climate change and create a sustainable energy future we urgently need to reduce energy use, by adopting more efficient technologies, and to generate energy from renewable sources, which release much less, or no, carbon dioxide into the atmosphere.
Renewable energy technologies, (such as wind, wave, tidal, hydro, solar and biomass - the growing and burning of crops for energy generation) can provide 'clean' carbon-free sources of energy, as an alternative to fossil fuels (gas/oil/coal), which traditionally dominate heating and electricity generation. (With the exception of Biomass energy, which does release carbon dioxide, but it is only returning to the atmosphere as much as was removed through photosynthesis during the plant's lifetime).
Burning fossil fuels, by contrast, returns carbon dioxide to the atmosphere which has been locked away in the Earth's crust for hundreds of millions of years). Supplies of fossil fuels are finite, and therefore their continued use is unsustainable. Renewable technologies are a sustainable method of energy generation as supplies of wind, wave, solar energy etc cannot, in effect, be depleted.