Climate Change

The ocean is key to achieving climate and societal goals

By Ove Hoegh-Guldberg, Eliza Northrop, Jane Lubchenco

Science 27 Sep 2019:
Vol. 365, Issue 6460, pp. 1372-1374
DOI: 10.1126/science.aaz4390

The just-released Intergovernmental Panel on Climate Change (IPCC) special report on the ocean and cryosphere in a changing climate (SROCC) (1) details the immense pressure that climate change is exerting on ocean ecosystems and portrays a disastrous future for most life in the ocean and for the billions of people who depend on it unless anthropogenic greenhouse gas (GHG) emissions are slashed. It reinforces in stark terms the urgency of reducing carbon emissions expressed in a 2018 IPCC report (2). But another just-released report (3) provides hope and a path forward, concluding that the ocean is not simply a victim of climate change, but a powerful source of solutions. Drawing on this report organized by the High Level Panel (HLP) for a Sustainable Ocean Economy, which quantifies and evaluates the potential for ocean-based actions to reduce emissions, we outline a “no-regrets to-do list” of ocean-based climate actions that could be set in motion today. We highlight the report's analysis of the mitigation potential and the required research, technology, and policy developments for five ocean-based mitigation areas of action: renewable energy; shipping and transport; protection and restoration of coastal and marine ecosystems; fisheries, aquaculture, and shifting diets; and carbon storage in the seabed (see the figure). Make no mistake: These actions are ambitious, but we argue that they are necessary, could pay major dividends toward closing the emissions gap in coming decades, and achieve other co-benefits along the way (34).

These five areas were identified, quantified, and evaluated relative to achieving the 2030 Agenda for Sustainable Development. The report concludes that these actions (in the right policy, investment, and technology environments) could reduce global GHG emissions by up to 4 billion tonnes of carbon dioxide equivalents in 2030 and by up to 11 billion tonnes in 2050. This could contribute as much as 21% of the emission reduction required in 2050 to limit warming to 1.5°C and 25% for a 2°C target. Reductions of this magnitude are larger than the annual emissions from all current coal-fired power plants worldwide. Considering each action area through a technical, economic, and social/political lens, the report concluded that carbon storage in the seabed requires considerable further investigation to address concerns regarding the impacts on deep ocean environments and ecosystems, but that the other four ocean-based sectors have substantial mitigation potential and could be readily implemented or initiated with the right policies, incentives, and guidance (3).

See full article at source: https://science.sciencemag.org/content/365/6460/1372

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The World’s Oceans Are in Danger, Major Climate Change Report Warns

By Brad Plumer

  • Sept. 25, 2019

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WASHINGTON — Climate change is heating the oceans and altering their chemistry so dramatically that it is threatening seafood supplies, fueling cyclones and floods and posing profound risks to the hundreds of millions of people living along the coasts, according to a sweeping United Nations report issued Wednesday.

The report concludes that the world’s oceans and ice sheets are under such severe stress that the fallout could prove difficult for humans to contain without steep reductions in greenhouse gas emissions. Fish populations are already declining in many regions as warming waters throw marine ecosystems into disarray, according to the report by the Intergovernmental Panel on Climate Change, a group of scientists convened by the United Nations to guide world leaders in policymaking.

“The oceans are sending us so many warning signals that we need to get emissions under control,” said Hans-Otto Pörtner, a marine biologist at the Alfred Wegener Institute in Germany and a lead author of the report. “Ecosystems are changing, food webs are changing, fish stocks are changing, and this turmoil is affecting humans.”

Read full article at source: https://www.nytimes.com/2019/09/25/climate/climate-change-oceans-united-nations.html

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In Ancient Oceans That Resembled Our Own, Mass Extinction Was Triggered By Oxygen Loss

by Zachary Boehm, Florida State University

Roughly 430 million years ago, during the Earth's Silurian Period, global oceans were experiencing changes that would seem eerily familiar today. Melting polar ice sheets meant sea levels were steadily rising, and ocean oxygen was falling fast around the world.

At around the same time, a global die-off known among scientists as the Ireviken extinction event devastated scores of ancient species. Eighty percent of conodonts, which resembled small eels, were wiped out, along with half of all trilobites, which scuttled along the seafloor like their distant, modern-day relative the horseshoe crab.

Now, for the first time, a Florida State University team of researchers has uncovered conclusive evidence linking the period's sea level rise and ocean oxygen depletion to the widespread decimation of marine species. Their work highlights a dramatic story about the urgent threat posed by reduced oxygen conditions to the rich tapestry of ocean life.

See Full Article at Source: https://phys.org/news/2019-03-ancient-oceans-resembled-oxygen-loss.html

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Oceans Have Absorbed 60% More Heat Than Scientists Thought

By Olivia Rosane

Nov. 01, 2018 07:00AM EST

The landmark report from the UN's Intergovernmental Panel on Climate Change published last month warned that humans needed to reduce greenhouse gas emissions 45 percent below 2010 levels by 2030 for us to have a shot at limiting global warming to 1.5 degrees Celsius above pre-industrial levels.

Now, another study published in Nature Wednesday found we might have even less time than that. This is because the oceans have been absorbing much more heat than previously calculated, meaning the earth is more sensitive to carbon dioxide emissions than scientists thought.

"We thought that we got away with not a lot of warming in both the ocean and the atmosphere for the amount of CO2 that we emitted," research leader and Princeton University geoscientist Laure Resplandy told The Washington Post. "But we were wrong. The planet warmed more than we thought. It was hidden from us just because we didn't sample it right. But it was there. It was in the ocean already."

How Much More Warming Is This?

In the past 25 years, the oceans have warmed 60 percent more than previously thought.

What Does This Mean?

It means that policy makers now have even less leeway when it comes to reducing greenhouse gas emissions if they want to keep warming to 1.5 or even 2 degrees above pre-industrial levels. The findings reduce the total amount of carbon dioxide humans can safely burn before crossing those thresholds by 25 percent.

They also have implications for the ocean-related impacts of climate change: the health of marine life and the pace of sea level rise.

Read Full Article at Source: https://www.ecowatch.com/oceans-heat-absorption-climate-change-2617077826.html

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Climate Change Indicators: Oceans

Covering about 70 percent of the Earth’s surface, the world’s oceans have a two-way relationship with weather and climate. The oceans influence the weather on local to global scales, while changes in climate can fundamentally alter many properties of the oceans. This chapter examines how some of these important characteristics of the oceans have changed over time.

Read the full article at source:  https://www.epa.gov/climate-indicators/oceans

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