Alaska melt ponds-NASA-Goddard

CLIMATE IMPACTS

IPCC Climate Report: Profound Changes Are Underway in Earth’s Oceans and Ice – a Lead Author Explains What the Warnings Mean

ROBERT KOPP / THE CONVERSATION – Humans are unequivocally warming the planet, and that’s triggering rapid changes in the atmosphere, oceans and polar regions, and increasing extreme weather around the world, the Intergovernmental Panel on Climate Change warns in a new report.

The IPCC released the first part of its much anticipated Sixth Assessment Report on Aug. 9, 2021. In it, 234 scientists from around the globe summarized the current climate research on how the Earth is changing as temperatures rise and what those changes will mean for the future.

We asked climate scientist Robert Kopp, a lead author of the chapter on Earth’s oceans, ice and sea level rise, about the profound changes underway.

What are the IPCC report’s most important overall messages in your view?

At the most basic level, the facts about climate change have been clear for a long time, with the evidence just continuing to grow.

As a result of human activities, the planet is changing at a rate unprecedented for at least thousands of years. These changes are affecting every area of the planet.

How do we know humans are causing climate change
Humans produce large amounts of greenhouse gas emissions, primarily through fossil fuel burning, agriculture, deforestation and decomposing waste. IPCC Sixth Assessment Report

While some of the changes will be irreversible for millennia, some can be slowed and others reversed through strong, rapid and sustained reductions in greenhouse gas emissions.

But time is running out to meet the ambitious goal laid out in the 2015 international Paris Agreement to limit warming to well below 2 degrees Celsius above preindustrial levels (2 C equals 3.6 degrees Fahrenheit). Doing so requires getting global carbon dioxide emissions on a downward course that reaches net zero around or before 2050.

What are scientists most concerned about right now when it comes to the oceans and polar regions?

Global sea level has been rising at an accelerating rate since about 1970, and over the last century, it has risen more than in any century in at least 3,000 years.

In the years since the IPCC’s Fifth Assessment Report in 2013 and the Special Report on the Ocean and Cryosphere in a Changing Climate in 2018, the evidence for accelerating ice sheet loss has become clearer.

Over the last decade, global average sea level has risen at a rate of about 4 millimeters per year (1.5 inches per decade). This increase is due to two main factors: the melting of ice in mountain glaciers and at the poles, and the expansion of water in the ocean as it takes up heat.

Ice sheets in particular are primarily responsible for the increase in the rate of sea level rise since the 1990s. There is clear evidence tying the melting of glaciers and the Greenland Ice Sheet, as well as ocean warming, to human influence. Sea level rise is leading to substantial impacts on coastal communities, including a near-doubling in the frequency of coastal flooding since the 1960s in many sites around the world.

global temperatures are rising
Global mean sea level change relative to 1900
The IPCC’s projections for global average sea level rise in meters with higher-impact pathways and the level of greenhouse gas emissions. IPCC Sixth Assessment Report

What’s more, the more the world limits its greenhouse gas emissions, the lower the chance of triggering instabilities in the polar ice sheets that are challenging to model but could substantially increase sea level rise.

Under the most extreme emissions scenario we considered, we could not rule out rapid ice sheet loss leading to sea level rise approaching 2 meters (7 feet) by the end of this century.

Fortunately, if the world limits warming to well below 2 C, it should take many centuries for sea level rise to exceed 2 meters – a far more manageable situation.

Are the oceans or ice nearing any tipping points?

“Tipping point” is a vague term used in many different ways by different people. The IPCC defines tipping points as “critical thresholds beyond which a system reorganizes, in a way that is very fast or irreversible” – for example, a temperature rise beyond which climate dynamics commit an ice sheet to massive loss.
Because the term is so vague, the IPCC generally focuses on characteristics of changes in a system – for example, whether a system might change abruptly or irreversibly – rather than whether it fits the strict dynamic definition of a “tipping point.”

One example of a system that might undergo abrupt changes is the large-scale pattern of ocean circulation known as the Atlantic Meridional Overturning Circulation, or AMOC, of which the Gulf Stream is part. Paleoclimate evidence tells us that AMOC has changed rapidly in the past, and we expect that AMOC will weaken over this century. If AMOC were to collapse, it would make Europe warm more slowly, increase sea level rise along the U.S. Atlantic coast, and shift storm tracks and monsoons. However, most evidence indicates that such a collapse will not happen in this century.

Will the Gulf Stream shut down
The Gulf Stream is part of the Atlantic Meridional Overturning Circulation. A slowdown would affect temperature in Europe and sea level rise along the U.S. East coast. IPCC Sixth Assessment Report

 
Robert Kopp is a professor in the Department of Earth & Planetary Sciences at Rutgers University and director of the Rutgers Institute of Earth, Ocean, and Atmospheric Sciences. He is a lead author of the Working Group 1 contribution to the Intergovernmental Panel on Climate Change’s Sixth Assessment Report.

Meet the Climate Corps

Angel Alguera, Rutgers Climate CorpsAngel Alguera
I am a first-year Atmospheric Science master’s degree student in the Department of Environmental Sciences, and my work focuses on meteorology and applications of climate change resiliency. My professional interests include severe weather forecasting and community preparedness regarding weather-related disasters. I work with Dr. James Shope at the NJ Climate Change Resource Center to produce applied research and reports relevant to New Jersey stakeholders. I currently assist with climate change data analysis, large dataset management, and report writing.

Benjamin GoldbergBenjamin Goldberg
I am a second-year Master of City and Regional Planning student concentrating in climate adaptation and resiliency planning, with experience in sustainable food systems. I joined the Climate Corps last summer to help develop a GIS-based food waste recovery tool, and currently support community resilience through flood vulnerability analysis. I hold a B.A. from Middlebury College and a Certificate in Ecological Horticulture from UC Santa Cruz.

Surya Jacob, Rutgers Climate CorpsSurya Jacob
I am a graduate student in the Master of City and Regional Planning program at the Bloustein School concentrating in community development, focused on housing, land and finance, as well as pursuing the Real Estate Development/Redevelopment Certification. Prior to Bloustein, I worked as an architect and interior designer in India and Canada and am pivoting towards a career in urban planning to engage in extensive projects at the macro level. My interests include affordable and mixed income housing, urban redevelopment, and housing finance, and I am deeply passionate about climate resilience in community planning. Being part of Climate Corps is a foundational step towards helping to solve equity issues in vulnerable communities along the coastal region.

Vineesh Das Kodakkandathil, RutgersVineesh Das Kodakkandathil
I am an urban planner with five years of professional experience in community-led ecotourism development and land use and environment management planning in ecologically sensitive areas. I have worked on and conducted extensive environmental sensitivity analyses, flood and landslide vulnerability assessments, and human impact assessments with the help of GIS tools. I’m currently pursuing my master’s in City and Regional Planning at Bloustein School with a concentration in Transport Planning and GIS.

Douglas LeungDouglas Leung
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Nihar MhatreNihar Mhatre
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Josephine O'GradyJosephine O’Grady
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Jessica Parineet Jessica Parineet
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Dillon Patel Dillan Patel
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Moira Sweeder, Rutgers Climate CorpsMoira Sweeder
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