study determines age of sea level rise

The work of American researchers has determined that the rise in sea level due to human activity began in the second half of the 19th century.

According to a study published in NatureCommunications and spotted by Futura, researchers have sought to determine when sea ​​level rise due to human activity had started. They felt that this dynamic had probably started between 1860 and 1870. That is emerging from a century of global Industrial Revolution in the United Kingdom, then in continental Europe and the United States.

To be more precise, this date corresponds to the time when sea level rise is outside the scope of natural variability (English speakers speak of “ToE” for Time of Emergence). This is an extremely important notion for studying the impact of man on his environment.

Distinguish human impact from normal and natural variations

Indeed, even independently of human activity, many parameters including sea level tend to change over time, often cyclically, and perfectly natural. This concept is called natural variability, and it poses a considerable challenge to researchers.

Because to estimate the impact of humans, it is fundamental to have a relatively precise idea of ​​this natural evolution. Otherwise, the impact of our species could be sometimes overestimated, sometimes underestimated. It would therefore be almost impossible to produce coherent climate models.

In this case, their work shows the phenomenon very clearly. The graph on the left clearly shows this natural variability; before 1700, the curve fluctuates, but remains fairly stable overall. On the other hand, the trend changes entirely from this period.

The Industrial Revolution, a critical tipping point

From 1760, the date of the start of the English industrial revolution, the new factories began to operate at full speed without anyone being aware of the ecological issues. Result: the level of atmospheric pollutants began to soar, which can be seen very clearly on the curve.

Less than a century later, the damage was already done; from 1873barely more than a century later, sea levels were already entirely out of natural variability. And this is only the date from which researchers have near certainty. Their statistical model, which can be seen on the graph on the right, suggests that the ToE could even be older. It could even date back to the very beginning of the Industrial Revolution.

Yet another booster shot

The study also concluded that sea level is not only far from the natural variability for a long time, but also that it is gone moving away faster and faster over time. Indeed, human-induced sea level rise has gone from a few tenths of a millimeter per year between 1700 and 1760 to about 1.4mm per year between 1940 and 2000which represents a very clear and far from negligible increase.

This work demonstrates once again the indisputable impact of human activity on sea levels. At the same time, they remind us of the urgency of the situation. If no decisive action is taken over the coming decades, the climate machine could run even further. We would then attend a new rise in power of the phenomenonas many models already provide, including those of the IPCC. And the urgency begins to be felt, knowing the massive impact that a few extra centimeters of water can have on coastal regions.

The text of the study is available here.

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