Global warming and pollution caused by humanity's carbon-heavy footprint are ravaging Earth's oceans and icy regions in ways that could unleash misery on a global scale, a landmark UN report to be unveiled next week will warn.
Diplomats and scientists from 195 nations gather in Monaco from Friday to validate a summary for leaders of observed and projected impacts ranging from vanishing glaciers and marine heatwaves, to rising seas and unprecedented levels of forced migration, according to a draft seen by AFP.
The underlying 900-page scientific report from the Intergovernmental Panel on Climate Change (IPCC) is the fourth such UN tome in less than a year, with others focused on a 1.5-Celsius cap on global warming, the decline of biodiversity, as well as land use and the global food system.
All four conclude that humanity must overhaul how it produces, distributes and consumes almost everything to avoid the worst ravages of global warming and environmental degradation.
The barrage of bad news from science and a newly alarmed public demanding decisive action are the backdrop for a key UN climate summit in New York on Monday designed to push countries into setting more ambitious carbon cutting goals.
Current pledges — if honoured — would see Earth's surface heat up more than three degrees Celsius above preindustrial levels. The 2015 Paris climate treaty calls for capping global warming at "well below" 2 C, and 1.5 C is possible.
A single degree of warming has already seen a crescendo of extreme weather, including killer heat waves and superstorms amped up by rising seas.
– Melting glaciers –
"Some of the impacts of climate change on our oceans are now irreversible and others are looking increasingly inevitable," notes Greenpeace International scientist, Melissa Wang.
"At current emissions rates, we are effectively dumping one million tonnes of CO2 into the oceans every hour."
Oceans and the frozen zones comprising the cryosphere cover more than 80 percent of Earth's surface, yet more money has been spent to explore the Moon.
The IPCC report pulls together thousands of peer-reviewed studies detailing not only how mankind has degraded the planet's seas and ice, but the blowback humanity will suffer as a consequence.
Since the mid-19th century, oceans have absorbed more than 90 percent of excess heat generated by the greenhouse gases that humans have dumped in the atmosphere.
Without oceans, human emissions would likely have warmed the planet's surface by at least 10 C more than today, according to a rough calculation by Katharine Hayhoe, an atmospheric scientist and director of the Climate Center at Texas Tech University.
Mountain glaciers in Asia and South America provide water for drinking and agriculture to nearly two billion people, and the stable weather patterns to which northern hemisphere populations have adapted depend on sea ice and ocean currents destabilised by global warming.
As the 21st century unfolds, melting glaciers will first give too much and then too little to billions who depend on them for fresh water, according to the draft report.
– Food chain disrupted –
Without deep cuts to manmade emissions, 30 to 99 percent of the northern hemisphere's surface permafrost could melt by century's end, unleashing billions of tonnes of planet-warming carbon.
By 2050, many low-lying megacities and small island nations will experience "extreme sea level events" every year, even under the most optimistic emissions reduction scenarios.
And by 2100, "annual flood damages are expected to increase by two to three orders of magnitude," or 100 to 1,000 fold.
Even if the world manages to cap global warming at two degrees Celsius — a big "if" — the global ocean waterline will eventually rise enough to submerge areas inhabited today by more than a quarter of a billion people, the draft report says.
"The migration crises we are witnessing in north Africa and Central America would pale in comparison to the repercussions of a 1.2 metre rise in sea level," Belize's Carlos Fuller, lead climate negotiator for the Association of Small Island States (AOSIS), told AFP.
Acidification is disrupting the ocean's basic food chain, and marine heatwaves — which have become twice as frequent since the 1980s — are creating vast oxygen-depleted dead zones.
The final advice to policymakers will be released on September 25.
While the underlying science cannot be modified, diplomats with scientists at their elbow will tussle over how to frame the findings, and what to leave in or out.
Climate change takes toll on oceans, ice: UN report
Paris (AFP) Sept 20, 2019 –
Humanity should brace for blowback from oceans and frozen zones increasingly addled by climate change, a major UN report will warn.
Loading the atmosphere with CO2 and greenhouse gases has spawned a host of consequences, starting with irreversible sea-level rise, according to a draft Intergovernmental Panel on Climate Change (IPCC) Special Report obtained by AFP.
Here are impacts highlighted in a summary slated for release on September 25:
– Oceans warming –
SOAK IT UP: Oceans have absorbed a quarter of manmade greenhouse gases and 93 percent of the extra heat they generate in the atmosphere. As a result, the world's seas have become warmer, more acidic and less salty.
HEATWAVES: The frequency, intensity and extent of marine heatwaves like those that devastated Australia's Great Barrier Reef have all increased, with ocean hot spells twice as likely today as during the 1980s.
EL NINOS: Extreme El Ninos — weather phenomena which drive forest fires, cause disease outbreaks and affect cyclones — are expected to double in frequency if emissions are not cut.
SUSTENANCE: Food supply from shallow tropical waters could decline by 40 percent by the year 2100 because of warming and acidification.
Some ocean wildlife populations — from minuscule plankton to big fish and marine mammals — have shifted hundreds of kilometres toward their preferred temperatures, adversely affecting coastal fisheries.
– Oceans rising –
SEA LEVEL: Compared to the 1980-2000 period, seas will rise nearly half a metre by 2100 if Earth warms 2C above preindustrial levels, and 84 cm in a 3C-4C world. In the 22nd century, the pace of sea-level rise is likely to jump 100-fold from 3.6 millimetres per year today to several centimetres annually.
Even if global warming is capped at 2C, oceans will eventually rise several metres, submerging areas that are today home to 280 million people.
FLOOD DAMAGE: Without major adaptation efforts, the cost of annual flood damage caused by storm surges would increase 100- to 1,000-fold by 2100.
ADAPTATION: Rising seas will force all coastal regions to adapt. Rich nations will more likely build barriers, developing ones will more likely be forced to retreat to higher ground.
NEW NORMAL: Many low-lying megacities and small island states will experience what are today rare sea-level extremes every year by 2050, no matter how fast CO2 emissions are drawn down.
WETLANDS: Globally, 20 to 90 percent of coastal wetlands will disappear by 2100, depending on sea-level rises.
– Oceans dying –
OXYGEN: The concentration of life-giving oxygen in marine environments has dropped two percent in 60 years, and will decline another three to four percent by 2100 at current rates of carbon pollution. Oxygen levels will likely decline over 59-80 percent of the ocean surface within 20 years.
DEAD ZONES: Coastal pollution and warming waters are creating vast oxygen-depleted dead zones.
CORALS: Coral reefs — a major bulwark against storm surges — will decline by 90 percent even in a 1.5 C world. Two degrees would be a death sentence for corals, which underpin the livelihoods of half a billion people today.
– Ice melting –
ICE SHEETS: Earth's two ice sheets, sitting atop Greenland and Antarctica, have shed on average more than 430 billion tonnes of mass each year since 2006, becoming the main drivers of sea-level rise.
GLACIERS: Average annual runoff from glaciers in most mountain regions will have peaked and begun to decline by 2100. Worldwide, more than two billion people today depend on glaciers for fresh water.
Low-altitude glaciers in the Alps, the Caucasus mountains and Scandinavia will lose more than 80 percent of current mass by 2100.
SNOW: Mountains will lose snow cover, with far-reaching impacts for agriculture, energy supply and tourism.
– Permafrost thawing –
PERMAFROST: Thirty to 99 percent of the world's top-layer permafrost — the top three metres — could melt by 2100 if carbon pollution continues unabated, releasing a carbon bomb of greenhouse gases. If emissions are aggressively capped, the area thawed could be vastly reduced.
HEAVY METAL: Toxic mercury and other "legacy contaminants" in drinking water will increase with the melting of glaciers and permafrost, which may store nearly 800,000 tonnes of mercury — twice the amount found in all other environments combined.
