DEMANDS for climate justice and declarations of a climate emergency have re-captured public and political attention, with two global movements gaining traction in recent months.

Last week, Extinction Rebellion protesters filled the streets of the UK, while children skipping school to protest for their future wellbeing has become a recurring weekly feature.

These movements come at a time when awareness of the effects modern human life can have on our planet is rising.

Images from the Open University (OU)/BBC co-production Blue Planet II have ingrained the environmental consequences of single-use plastics on the public imagination.

The latest Intergovernmental Panel on Climate Change (IPCC) report on a global warming scenario of 1.5C shows we’re at a critical moment for ensuring human-induced climate change does not exceed that figure over the next century if we are to protect and maintain ecosystems, infrastructure and food security.

Humans are creatures of comfort. Understanding the effects of climate change, and how to mitigate against it, is in our interests to ensure that comfort. We know this at least in part because when we look back, the fossil record presents evidence that not all our ancestors were able to retain a “comfortable” life – sometimes due to dramatic changes in Earth’s climate.

It was during the Scottish Enlightenment that the scientist James Hutton, one of the founders of geology, identified the need to study Earth’s natural history as a means to understand Earth’s processes, now and in the future. Scientists today follow in Hutton’s footsteps, seeking to reconstruct Earth’s past climate history in order to predict and project how Earth might respond to climate changes in the future.

A natural library of information lies beneath our feet: tales of past ice ages, mass extinctions and periods of extreme climatic warmth millions of years ago can be found deep in the ocean. The International Ocean Drilling Program (IODP) emerged following the advent of ocean drilling in the 1960s. The space race was at its peak and scientists were not only motivated to reach the outer limits of Earth, but its inner depths. The development of ocean-drilling technology enabled scientists ever since to recover deep-sea mud records from the ocean floor so they can study past climate.

An expedition to the Bay of Bengal by the IODP in late 2014 recovered deep-sea sediment cores (the aforementioned mud records) with the aim of providing an improved understanding of how the Indian Monsoon behaved in the past. The monsoon is a significant feature of Earth’s climate due to the huge amount of rainfall it brings to some of Earth’s most densely populated regions.

During the summer, in our hemisphere, the sun heats up the Asian continent and increases the difference in heat between the land and ocean. This drives a shift in prevailing wind direction; winds begin to blow across the Indian Ocean, picking up moisture, which is then rained out over the Indian subcontinent. Greater rainfall during the summer monsoon feeds the river systems draining into the Bay of Bengal.

The ocean surface in the Bay of Bengal freshens during the summer monsoon thanks to that increased rainfall and river runoff and this is preserved in the shells of microscopic fossils found in ocean muds, and recovered during the IODP expedition.

These fossils, the size of a sand grain, lived in the surface waters of the Bay of Bengal thousands of years ago. As their shells grew, the chemistry of the seawater was locked in, providing a snapshot of past ocean salinity and temperatures, which can be used to construct records of historical monsoon strength.

Mud samples recovered from the IODP expedition were washed over sieves to isolate the tiny fossils. Some of these fossils were picked for chemical analyses. These analyses enabled extraction of the past signals of salinity and temperatures. The records of past monsoon strength produced from these fossils are then compared with other climate records to build a global picture of past climate events.

The past million years have seen the climate fluctuate between cold glacial periods with extensive ice-sheets and warm interglacial periods with reduced ice-sheets. We are currently in an interglacial period; some 18,000 years ago the last ice-age began to deteriorate. This period of Earth’s history is relatively well understood. However, understanding of how Earth’s internal climate system responded to the previous deglaciation, around 128,000 to 140,000 years ago, is less well-known.

Ice-core records show Antarctica was first to respond to climate warming, around 140,000 years ago.

This warming in the south was a source of heat and moisture which fuelled a strengthening of the Indian monsoon. This predated global climate warming in the rest of the northern hemisphere.

It’s thought the Indian Monsoon acted as a channel communicating warming in the southern hemisphere to the northern hemisphere by transporting heat and moisture.

But changes in the Indian Monsoon due to human-induced climate changes may also have significant impacts on global climate, because the elements of Earth’s climate are innately connected.

The latest IPCC report shows predictions regarding future behaviour of the monsoon remain incredibly uncertain, limiting our ability to act. Looking for answers in the past remains critical, and perhaps some of the answers we need remain buried in these ocean muds.

Katrina Nilsson-Kerr is a PhD student at The Open University, specialising in palaeoclimatology