Cause

The Earth's Climate Is Changing

The Earth's climate is shifting after more than 10,000 years of very stable conditions—the duration of human civilization. According to climate science, when average temperatures rise, acute hazards like heat waves and floods become more frequent and severe, while chronic hazards like drought and rising sea levels become more severe. The research explores physical risk as the foundation of both transition and liability risks in order to better understand the nature and scope of physical risk from a changing climate over the next one to three decades.

Global mean sea level is rising as a result of global warming in two different ways. First, ice sheets and glaciers around the planet are melting and replenishing the ocean with water. Second, as the water gets warmer, the ocean's volume grows. Aquifers, lakes, reservoirs, rivers, and soil moisture all contain liquid water; their loss is a third, much less significant cause of sea level rise. Groundwater pumping is largely to blame for this movement of liquid water from the land to the ocean.

Global Sea Level Change - Why It Matters?

Since 1880, the average sea level has increased by around 8 to 9 inches (21 to 24 centimeters). The melting of glaciers and ice sheets and the thermal expansion of warm seawater are the main causes of the rising water level. Global mean sea level reached its highest yearly average in the satellite record in 2021, rising 97 millimeters (3.8 inches) above 1993 levels (1993-present).

Between 2006 and 2015, the average global ocean water level increased by 0.14 inches (3.6 millimeters) each year, which was 2.5 times the average growth rate of 0.06 inches (1.4 millimeters) per year during the majority of the 20th century. Global mean sea level is predicted to increase by at least one foot (0.3 meters) above 2000 levels by the end of the century.

Acceleration of Ice Loss - Melting Ice Sheets and Glaciers

The world’s glaciers are losing 267 gigatonnes of ice per year, driving a fifth of global sea level rise.

Melting and heat expansion were about equal contributors to the observed sea level rise starting in the 1970s and continuing over the last ten years or so. However, the pace of mountain glacier and ice sheet melting has increased:

Over the past few decades, the decadal average loss from glaciers in the reference network of the World Glacier Monitoring Service has quadrupled, rising from the equivalent of 6.7 inches (171 millimeters) of liquid water in the 1980s to 18 inches (460 millimeters) in the 1990s to 20 inches (-500 millimeters) in the 2000s to 33 inches (850 millimeters) for the decade of 2010 to 2018.
Between 2012 and 2016, the Greenland Ice Sheet's ice loss rose seven-fold, from 34 billion tons annually between 1992 and 2001 to 247 billion tons annually.
The loss of Antarctic ice doubled between 2012 and 2016 from 51 billion tons per year between 1992 and 2001 to 199 billion tons per year.

As a result, from 2005 to 2013, the amount of sea level rise caused by melting was rough twice as great as the amount caused by thermal expansion (with a minor addition from groundwater transfer and other water storage movements).

A Weakened Jet Stream - Obstruction of Ocean Currents and Air Circulation

Jet Streams are Fast-moving belts of wind that take wavy, meandering paths around the planet.

The temperature difference between southern and northern air is starting to narrow as a result of the Arctic warming more quickly than the rest of the planet, which weakens the jet stream. This explains why persistent weather systems continue to hit one area hard while completely ignoring others.

Currents get weaker as temperatures rise. Simply put, the water won't be able to circulate as well if the water at the poles is not as cold and dense. Additionally, freshwater is being poured into the salty ocean as a result of the melting of the Greenland continental ice sheet, changing the density of the water masses once more.

The Greenland ice sheets are melting in this area of the ocean, which is causing sea levels to increase while also slowing circulation.

This suggests that the slowing is most likely the effect of human influence rather than a natural shift. Evidence indicates a persistent weakening of the Atlantic Meridional Overturning Circulation, which has a significant impact on global climate, particularly in North America and Europe.

In Consequence - Extreme Weather Event Attribution

Combining the evidence over the past 20 years, the literature is heavily dominated by studies of extreme heat (30%), rainfall or flooding (25%), and drought (16%). Together, these makeup more than two-thirds of all published studies (71%).

As the chart shows, the number of extreme events studied has grown substantially over the past 10-15 years.

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