Historians often rely on new discoveries in order to make breakthroughs. Every now and again, a fresh document, a set of papers or a whole manuscript is found by chance. Maybe something unexpected and surprising will pop up from an archaeological dig or – in the case of inns and oasis towns along the Silk Roads – from the declassification of CIA satellite images taken during the cold war, which revealed sites that had long fallen out of use and been forgotten on the ground.

Researchers used to dream about such treasure troves. They do not have to any more. We are living not so much in a golden age of new evidence, but in one of hyper-abundance. Almost all of this comes from the physical and natural sciences. Politicians often talk crudely about “choices” between the humanities and Stem subjects, but in today’s world, cutting-edge history is all about understanding, assessing and integrating materials from sources that would have been completely alien to most historians writing just a generation ago. These materials are transforming ideas about the past – often in radical ways. And climate is central to that transformation.

That’s the case because so many of these new sources are linked to “climate archives” – data that can be collected from the analysis of tree rings, by measuring calcium carbonate deposits in caves or by assessing carbon dioxide bubbles and impurities in ice cores drilled in Greenland, the Antarctic and elsewhere. These not only reveal atmospheric composition, but also indicate levels of human activity: for example, lead particles recovered from polar regions tell us that more energy was used in ancient Rome than in any other era before the start of the Industrial Revolution.

The insights such materials provide are not only exciting but essential to how we think about the past. One of the key factors in the fall of Cleopatra, for example, appears to have been the massive eruption of the Okmok volcano in Alaska in 43BC, an event that can now be measured scientifically but which also corresponds with contemporary accounts of feeble sunlight and reports of crop shortfalls. This produced a local crisis that included famine, migration, inflation and land abandonment – all of which put the Egyptian ruler in a precarious position that she tried to solve by deciding to throw her lot in with Mark Antony, with fateful consequences.

Eruptions help explain other major changes, such as the emergence of a “super-elite” in Scandinavia. The collapse of exchange networks and depopulation that followed volcanic activity made land cheaper, and consequently formed the basis not only for large-scale land ownership, but for the age of the Vikings. Or there is the famous case of Mount Tambora, whose eruption in 1815 brought about a “year without a summer”. This not only created the atmospheric conditions that inspired Mary Shelley to write Frankenstein while holidaying in an unusually cold and stormy Switzerland, but led to agrarian collapse in New England and prompted the first major economic depression in the history of the United States.