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In this update:

1.5-degree Celsius warming – when? The Oceans decide

Atlantic Hurricane Season Outlook Above Normal

Sea level rise of up to 1 m for the North Sea

Warming increases precipitation extremes

Record low levels of global sea ice

 

June 2017 - Download the Science Update #1 as a PDF

 

1.5-degree Celsius warming – when? The Oceans decide

In many ways, the oceans are the memory of the Earth’s climate system. A warm year at a particular location will for instance set its imprint on part of the ocean. Via the ocean currents, this signal will be transported to other places, where it will be relieved back to the atmosphere up to decades later. Changes in these ocean processes could mean that we reach the 1.5°C global warming level several years sooner than anticipated.

Recent climate model predictions suggest a turnaround in this slow-moving natural oscillation in the climate system, called the Interdecadal Pacific Oscillation (IPO), meaning a sustained period of rapid temperature rise might be underway. If the Pacific Ocean moves to a positive IPO phase, this could mean global warming will exceed 1.5°C already around 2026, while the negative IPO predicts this to happen in 2031.

Given the short time span until2026, the probability of stabilising the temperature increase at 1.5°C or even 2°C seems more remote than ever.

“Policymakers should be aware of just how quickly we are approaching 1.5°C. The task of reducing emissions is very urgent indeed.”

Henley, B. J., and A. D. King in "Trajectories toward the 1.5°C Paris target: Modulation by the Interdecadal Pacific Oscillation"

This figure shows observed global annual mean surface temperature anomaly and modelled future temperature anomalies. The red and blue dotted lines show when the ensemble mean will breach the 1.5°C Paris target. Source: Henley and King (2017).

 

Hurricane Season Outlook Above Normal

Forecasters at NOAA’s Climate Prediction Center say there is a 45% chance that the Atlantic sees another above-normal hurricane season this year, which means bad news for owners of coastal facilities and properties. The forecasters predict a 35 percent chance of a near-normal season, and only a 20 percent chance of a below-normal season. The season runs from June through November, but the numbers include Tropical Storm Arlene, a rare pre-season storm that formed over the eastern Atlantic in April. “The outlook reflects our expectation of a weak or non-existent El Niño, near- or above-average sea-surface temperatures across the tropical Atlantic Ocean and Caribbean Sea, and average or weaker-than-average vertical wind shear in that same region,” said Gerry Bell, lead seasonal hurricane forecaster.

 

 

Sea level rise of up to 1 m for the North Sea 

Future extreme sea levels and flood risk along European coasts will be strongly impacted by further global warming. Sea level rise, tides, waves, and storm surges will together increase between 57 and 81 cm on average by the end of the century, according to analysis based on two of the IPCC scenarios (RCP4.5 and RCP8.5). The North Sea region is projected to face the highest increase, amounting to nearly 1 meter, under a high emission scenario by 2100, followed by the Baltic Sea and Atlantic coasts of the UK and Ireland. Sea level rise is the main driver of the changes, but intensified climate extremes in Northern Europe can have significant local effects. By the end of this century, 5 million Europeans could be at risk annually from coastal flooding in a high-end warming scenario.

 

Warming increases precipitation extremes

It is a well-known prediction from climate models that wet regions will become wetter and dry regions dryer due to global warming. This is now also confirmed through evidence from the past. Two scientists, Aaron E. Putnam and Wallace S. Broecker from University of Maine and Colombia University, respectively, have studied ancient lake beds, cave stalagmites and ice corings. These data confirm that the temperature difference between the Northern and Southern hemisphere will drive the planet’s rainbelts northwards, at least during the winter months. During summer, the tropics will become wetter, while the subtropics and the mid-latitudes will become drier.

 

Record low levels of global sea ice

We hit a new low point last winter with the smallest extent of global sea ice ever recorded. While the sea ice in the Arctic is on a relatively stable slope downwards, it was in the south, in Antarctica, that the dramatic action was observed starting in October last year. The abrupt decrease last fall and winter was probably due to a weakening of the winds in the region, while climate change is expected to contribute to a long-term decline. Still, the remarkable breakaway of the sea ice curve serves as a reminder that things are happening extremely fast in both Polar Regions and faster than most climate models and the IPCC predicts.