marine heat waves – The Front Page

Highlighting Key Sessions at AMS 2025

A symposium at the 105th Annual Meeting of the American Meteorological Society will honor Gerald (Jerry) Meehl, a nationally and internationally recognized leader in climate dynamics, climate change, climate modeling and Earth system predictability, and present cutting-edge science in his areas of expertise. Meehl is currently a Senior Scientist at the NSF National Center for Atmospheric Research (NCAR), section head of the Climate Change Research Section, and the Principal Investigator/Chief Scientist for the DOE-NCAR Cooperative Agreement To Analyze variabiLity, change and predictabilitY in the earth SysTem (CATALYST) project.

We spoke to Gerald A. Meehl Symposium Co-Chair Aixue Hu, Project Scientist in the Climate and Global Dynamics Lab at NSF NCAR, about the field, Dr. Meehl, and what to expect during the symposium, which takes place Tuesday, 14 January, 2025.

“Jerry is a living, breathing encyclopedia of the history behind the history of climate science.”
–Maria Molina, NSF NCAR/University of Maryland

What can attendees expect from the Symposium?

This symposium will honor Dr. Meehl’s service to the climate research community (including his contributions to the CMIP and IPCC assessment reports); and will highlight the current state of research on climate variability, predictability, and change.

Presentations will discuss topics including extreme events, climate dynamics, marine heat waves, subseasonal to decadal climate prediction and predictability, AI and machine learning in climate research and prediction, and interactions between internal variability and external forcings – along with current modelling efforts and the future directions of model improvements.

Why is this such an important field right now?

The global mean temperature continues to rise, and most of the hottest years on record have appeared in the most recent decade. This change in the mean background climate can result in significant impacts on accurate weather forecasts, and on subseasonal to seasonal to decadal predictions. For example, with a much warmer mean climate, the chance for extreme weather events (heat waves, hurricanes, extreme precipitation) increases. Society benefits from improving our understanding of how this change in mean climate will affect our capability to accurately predict/forecast the weather on shorter timescales, and ENSO and decadal climate modes on longer timescales.

How would you summarize Jerry Meehl’s impact on the field so far?

Over the years, Jerry has spearheaded several new research directions focused on climate models. For example, his work has greatly advanced our understanding of the global warming slowdown in the early 2000s (the “hiatus”) and explored its predictability. His pioneering 2011 Nature Climate Change paper on this topic was named one of the five most influential papers in the first five years of Nature Climate Change (2016). His work has also been crucial to the study of extreme temperature events, monsoons, and decadal climate variability and predictability.

Jerry chaired the Coupled Model Intercomparison Project (CMIP) Panel under the World Climate Research Program (WCRP) from 1997 to 2007. He led the formulation of the CMIP1 through CMIP3 projects and continued to serve on the panel as it formulated CMIP5 and 6. CMIP1-3 provided the physical science foundation for the Intergovernmental Panel on Climate Change’s (IPCC) AR3 and AR4 reports.

A historic workshop held at Scripps in 1994 convened the global coupled modeling community to help formulate CMIP; Meehl is pictured second from left, in the second row from the bottom; also pictured: Ron Stouffer (4^th from left), Karl Taylor (5^th from left), Ben Santer 6th from left. Photo courtesy of Gerald Meehl.

Dr. Meehl also chaired the WCRP Working Group on Coupled Models (2004-2013) and the National Academy of Sciences/National Research Council Climate Research Committee (2008-2011), among other prominent national and international committees. He was a contributing, coordinating, or lead author for the IPCC AR1-AR5 reports, and a member of the IPCC science team that was awarded the 2007 Nobel Peace Prize.

Photo: Author team for Chapter 10, “Global Climate Projections,” IPCC Fourth Assessment Report (AR4), Christchurch, NZ, 2005; coordinating lead authors Jerry Meehl and Thomas Stocker are center back. Photo courtesy of Jerry Meehl.

The AMS has recognized Jerry’s scientific contributions to, and leadership in, climate research, awarding him the Jule G. Charney Award in 2009 “for outstanding collaborative contributions to modeling climate and its response to anthropogenic and natural forcings” and the Sverdrup Gold Medal in 2023 “for seminal work integrating observations, models, and theory to understand variability and change in the ocean and atmosphere.” He is also a fellow of AMS since 2006, and of AGU since 2014. He has also been recognized by organizations including Reuters and Web of Science as an influential and very highly cited researcher.

Left photo: Jerry Meehl and Warren Washington awarded the AMS Charney Award, in Phoenix, AZ (2009). Right photo: Group photo of participants in the Warren Washington Symposium at AMS, January 2010, convened by Dave Bader and Jerry Meehl; the only time that “legends of climate modeling” Suki Manabe, Larry Gates, Warren Washington, and Jim Hansen attended the same meeting at the same time. From left: Kirk Bryan, Suki Manabe, Jerry, Greg Jenkins, Larry Gates, Jane Lubchenco, Steve Schneider, Dave Bader, Warren Washington, John Kutzbach, V. Ramanathan, Jim Hansen, Bert Semtner. Photo credits: American Meteorological Society.

Even as a world famous climate scientist, Jerry is very approachable. He makes himself available to young scientists and gives them unselfish guidance and support. When Jerry was leading the CMIP effort and was lead author for the IPCC assessment reports, his communication skills helped move the CMIP effort forward, and he navigated through differences among lead authors smoothly. Jerry is not only a great scientist, but also a great mentor, communicator, and writer. He has worked with numerous graduate students, post-docs, and junior researchers and left significant impacts on their careers. That includes being my own mentor and role model for over 20 years!

It might be a surprise to many people, especially the early career scientists, that Jerry is also a writer. He has authored and co-authored six books that grew out of his personal interests in World War II, especially in the Pacific theater. His ability to communicate and relate to others shines through no matter what he does!

The Gerald A. Meehl Symposium will be held Tuesday, 14 January, 2025 at the AMS 105^th Annual Meeting, in New Orleans, LA, and online. Learn more about the Symposium and view the program.

Earth hit record highs in global temps, greenhouse gases, sea level, and more last year.

By AMS Staff

Last year, global high temperatures, warm oceans, and massive wildfires broke records and sparked increasing concern about climate change. Now the annual State of the Climate report, produced by the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information (NCEI) and peer reviewed and published by the American Meteorological Society, gives us an in-depth global picture of 2023, a year of extremes.

According to the NOAA/AMS press release, the State of the Climate report this year includes contributions from more than 590 scientists from 59 countries, and “provides the most comprehensive update on Earth’s climate indicators, notable weather events, and other data collected by environmental monitoring stations and instruments located on land, water, ice and in space.”

Below are a few highlights from 2023.

Record-high greenhouse gases (again)

Global atmospheric carbon dioxide, methane, and nitrous oxide all reached higher concentrations than ever recorded. CO₂ was 419.3±0.1ppm, 2.8 ppm higher than in 2023 and 50% higher than pre-industrial levels. This is the fourth-largest recorded year-to-year rise in CO₂.

Record-high global temperatures

2023 officially beat 2016’s record as the hottest year overall since records began in the 1800s, partly due to the transition from La Niña to a strong El Niño. Globally, 2023 was 0.99°–1.08°F (0.13°–0.17°C) above the 1991–2020 average. The years 2015–2023 have been the hottest nine years on record.

Global Surface Temperatures Were Above Average Across Most of the World (Plate 2.1a in State of the Climate in 2023): During 2023, much-warmer-than-average conditions were observed across most of the world’s surface, with the largest positive temperature anomalies across parts of the higher northern latitudes, shown here as areas shaded from orange to red. Limited areas experienced near-average to cooler-than-average conditions (blue shading). *[Note: graphic shows 2023 average temperature anomalies above or below the 1991-2020 average global temperature.]*

North America overall experienced its warmest year since records began in 1910, including a heat wave in Mexico that killed 286 people. The Caribbean also experienced its warmest recorded year, and Europe its warmest or second-warmest depending on the analysis.

In Kyoto, Japan, the cherry trees reached peak bloom on March 25, the earliest bloom in the city’s 1,200-year record. Photo: Balazs Simon on Pexels.

Record-high ocean heat

El Niño also contributed to the hottest oceans ever recorded. Mean annual global sea-surface temperature was 0.23°F (0.13°C) higher than 2016’s previous record, and August 22, 2023 saw an all-time high daily mean global sea-surface temperature of 66.18°F (18.99°C). Marine heat waves were recorded on 116 days of 2023 (vs. the previous record of 86 days in 2016) and global ocean heat content down to 2,000 feet also reached record highs.

Record-high sea levels (again)

Global mean sea level rose 8.1±1.5 mm in 2023, to reach a record 101.4 millimeters above the average from 1993, when satellite measurements began.

Massive wildfires caused by heat and drought

37 million acres of Canada burned in 2023, twice the previous record, causing evacuations for more than 232,000 people and with smoke affecting cities as far away as western Europe. Australia experienced its driest August–October since 1900, leading to millions of acres burned in bushfires in the Northern Territory. The European Union experienced its largest wildfire since 2000 (in the Alexandroupolis Municipality of Greece). Notable wildfires also occurred in Brazil, Paraguay, and in the U.S. state of Hawaii.

Warm poles and a greener Arctic

2023 was the fourth warmest year in the Arctic in the 124-year record, and the warmest recorded June–September. Sea ice reached its fifth-lowest extent in the 45-year record (with many monthly and daily records set), and multi-year ice declined. Despite above-average spring snowpack in the North American and Eurasian Arctic, rapid melting led to record and near-record lows in snow-water equivalent by June. The Northern Sea Route and Northwest Passage both opened, and the Northwest Passage saw a record 42 ship transits. Arctic tundra vegetation reached its third-greenest peak in the 24-year record.

Much of Antarctica also experienced well-above-average heat. In addition, eight months, and 278 days, saw record lows in sea ice extent and area in Antarctica; daily sea ice extent on 21 February was the lowest ever recorded.

*Clean infrared image of Hurricane Otis making landfall near Acapulco, Mexico. Image captured on 25 October, 2023, at 5:20 UTC, by the ABI instrument aboard the GOES-East satellite. Source:* *NASA Worldview*.

Below-average tropical cyclone activity, yet notable storms

There were 82 named tropical storms in 2023, below average. However, global accumulated cyclone energy was above average, rebounding from 2022’s record low, and there were seven Category 5 cyclones. Tropical Cyclone Freddy became the longest lived tropical cyclone on record, lasting from February 6 to March 12; it made landfall three times and caused 165 fatalities in Mozambique and 679 fatalities in Malawi due to flooding and landslides. Typhoon Doksuri/Egay was the costliest economically, causing US$18.4 billion in damages; Beijing saw its heaviest recorded rainfall and 137 residents died in flooding. Rain and floods from Storm Daniel killed at least 4,300 people in Libya. Hurricane Otis underwent the most extreme rapid intensification on record—Category 1 to Category 5 in only nine hours—and became the strongest landfalling hurricane to hit western Mexico, devastating Acapulco.

Persistent ozone hole

The stratospheric ozone hole over Antarctica appeared earlier in the year and lasted longer than normal, and reached its 16th largest extent in 44 years.

The full State of the Climate report includes regional climate breakdowns and notable events in every part of the world. Read the full 2023 report here. Read a summary of key takeaways here.

Image at top: Ice Worm Glacier in the North Cascade mountains of Washington, United States, which was under continuous annual monitoring from 1984 onward and disappeared in 2023. Large photo: The location of former Ice Worm Glacier on 13 August 2023. Inset photo: Ice Worm Glacier on 16 August 1986. Photo credits Mauri Pelto.

Be There: The Gerald A. Meehl Symposium