Venus, Earth, and Mars are approximately at the same distance from the Sun. This means they formed out of the same material and had approximately the same initial temperatures 4.6 billion years ago. Long ago these three planets probably had moderate enough temperatures suitable for life. However, Venus is now much too hot for life and Mars is too cold for life. However Earth has the perfect temperature not too hot or too cold, just right. This is known as the Goldilocks effect. The conditions needed for life are; right temperature, water, oxygen, sunlight, suitable climate and gravity. Earth fulfils all of these things, but Mars and Venus only fulfil a few of these things. This comes back to the point about The Goldilocks effect. The greenhouse effect plays a big role on these things. The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. Greenhouse gases include water vapour, carbon dioxide, methane, nitrous oxide, ozone and some artificial chemicals such as chlorofluorocarbons (CFCs). The absorbed energy warms the atmosphere and the surface of the Earth. This process maintains the Earth’s temperature at around 33 degrees Celsius warmer than it would otherwise be, allowing life on Earth to exist. The problem we now face is that human activities – particularly burning fossil fuels (coal, oil and natural gas), agriculture and land clearing – are increasing the concentrations of greenhouse gases. This is the enhanced greenhouse effect, which is contributing to warming of the Earth. With an enhanced greenhouse effect, the Earth is unable to release enough heat to space which leads to global warming. Global weather patterns absorb some of this overall increase in temperature and adjust for this accumulation in energy. These two effects are now creating climate changes around the world.Scientist have recorded a 0.75°C increase in the planet's overall temperature during the course of the last 100 years.