As BBC reported, science teams reconstructed the climate conditions that occurred during the last 2,000 years using 700 proxy records of temperature changes, including tree rings, corals and lake sediments. They found out that none of these climate events happened on a global scale.
In fact, any longer-term peaks or troughs in temperature were observed in no more than half the globe at any one time. On the other hands, current warming affects the vast majority of the world, in fact 98% of the world.
What is more, before the modern industrial era, the most significant influence on climate was volcanoes, while there were no variations in the Sun's radiation, which impacted global temperatures. Now however, the warming exceeds natural variability.
These findings indicate that the main reason for this warming are people, with many experts saying that this new work debunks many of the claims made by climate sceptics in recent decades.