Climate change is sometimes referred to as "global warming," a phrase that describes the overall average temperature increase around the world.
Evidence for climate change is fairly straightforward. On average, the world is now more than 1.5 degrees Celsius warmer than it was early in the twentieth century. Scientists can point to short-term temperature increases, notably record high temperatures by month, as evidence of global warming as well.
Of course, the planet has witnessed many periods of global warming and cooling. These can be measured by looking at sedimentary rock, tree rings, and many other sources. Scientists point out, however, that what makes this particular climate trend unique is that it is the result of human activity.
Scientists have established with near-certainty that higher levels of greenhouse gases, a consequence of burning fossil fuels, are to blame for current climate patterns. These changes are also occurring at much faster and more severe rates than previously recorded climate shifts. In short, fossil fuels, the energy source for the Industrial Revolution and for many other modern advances, are the main culprit in bringing about climate change.
In terms of human responses, scientists generally agree that abrupt and thorough reductions in consumption of fossil fuels are essential to changing the current climate trend. Societies must turn to cleaner forms of energy, to less fossil fuel-intensive industrial and agricultural practices, and they must do so rapidly.