A Conversation with Dr. John Kennedy, Lead Author of the State of the Global Climate 2024

By John Kennedy 23 April, 2025

WMO's latest report confirmed that 2024 was likely the first calendar year to be more than 1.5°C of warming above pre-industrial levels. We speak with Dr. Kennedy, lead author of the report, to unpack the alarming findings

In 2024, concentrations of key GHG & ocean heat content hit record levels; The past 3 yrs also saw the largest loss from reference glaciers around the world + all this contributed to record high global mean sea levels
Glaciers are important for Asia because they supply water for ~220mn people downstream; However many of these glaciers are far from equilibrium & will keep losing mass for decades even if we stop emitting tomorrow
SLR will bring cascading impacts to coastal areas, however impacts will depend on its levels & adaptation measures; Report highlights the importance of adequate multi-hazard early warning systems - which only half of all countries have
Author: John Kennedy
John is a British scientist working on climate change. He received his bachelor’s and master’s degrees in Natural Science from the University of Cambridge in the UK and completed a PhD in high-energy physics at the University of Liverpool. He worked for the Met Office in the UK for 18 years, working on climate monitoring and climate data set development, and is currently working as a climate consultant in France. John is co-chair of the WMO Expert Team on Monitoring and Communicating Climate Variability and Change and has been the scientific coordinator for the annual WMO State of the Global Climate reports since 2018.
Read more from John Kennedy →

The World Meteorological Organization’s State of the Global Climate report confirmed that as of 2024 we have likely seen the first calendar year to be more than 1.5°C above pre-industrial levels. Whilst the planet is issuing more distress signals, the report still highlights that limiting long-term warming to 1.5°C is still possible, but leaders must step up. To find out more, we sit down with John Kennedy, the lead author of the report, as he breaks down the report’s key findings, the dangers of triggering irreversible impacts, key advice plus more.

CWR: Thank you for joining us today. Congratulations on the recent publication of the State of the Global Climate 2024 report. Can you give us a rundown of the report’s key findings?

Dr. John Kennedy (JK): Thank you for the opportunity to talk about the report. The report shows that concentrations of key greenhouse gases continued to increase in the atmosphere reaching new record high levels. As a consequence, energy continued to accumulate in the climate system. Most of this goes into the ocean and we saw record ocean heat content in 2024.

Concentration of key GHG & ocean heat content hit record levels…

…the past 3 yrs also saw the largest loss from reference glaciers around the world…

…+ all this contributed to record high global mean sea levels

The past three years saw the largest three-year loss from reference glaciers around the world. Both of these factors – ocean heat and glacier mass loss – contributed to record high global mean sea level. We also saw low sea ice extents in both the Arctic and Antarctic and continued acidification of the ocean. These broad scale changes in the climate – together with the long-term increase in global temperature – are all interlinked and stem ultimately from human emissions of greenhouse gases.

What stood out to me in 2023 and again in 2024 was just how high global temperatures were and, indeed, how high they continue to be in the first months of 2025.

The report also highlights the continued vulnerability of people around the world to extreme weather and climate events.

CWR: Many of us in Asia may not realise why glacier loss is important, as it often feels “out of sight and out of mind”. But can you tell us why this will impact us?

Dr. JK: Glaciers are often referred to as the water towers of the natural world as they are an important source of water for human and natural systems. In Asia, glaciers provide water resources for around 220 million people living in downstream areas.

Glaciers supply water for ~220mn people in Asia downstream…

…however many of these glaciers are far from equilibrium & will keep losing mass for decades even if emissions stop tomorrow

The long-term changes in water supply from loss of glacier ice can also affect agriculture and hydro-electric power generation. The high-elevation area around the Tibetan Plateau contains the largest volume of ice outside of the polar regions and most (though not all) of the glaciers in the region have been retreating over the last several decades. This loss of ice from glaciers is contributing to global sea level rise, which affects populations in coastal areas far from the glaciers. Even if emissions of greenhouse gases were to stop tomorrow, glaciers in many places are far from equilibrium and would continue to lose mass for decades or even longer.

CWR: The report highlights the critical state of our oceans if warming persists. Some of these impacts might be irreversible for “hundreds, if not thousands of years”. Can you expand on what this means?

Dr. JK: Around 90% of the excess energy trapped by human emissions of greenhouse gases goes into the ocean. That energy warms the ocean, and we see that in the increase of ocean heat content and, because the ocean covers 70% of the Earth’s surface, global temperature. In a sense, by absorbing the majority of the energy, the ocean acts as a buffer, moderating global warming.

~90% of excess energy trapped by emissions goes into the ocean…

…so even if we stop emitting, ocean warming + SLR will continue for hundreds & thousands of yrs…

It can do this because the ocean has a large heat capacity – it takes a lot of energy to warm water – and also because the ocean is large and deep – there’s a lot of it to heat up. On the other hand, because of these same factors, it takes thousands of years for the deep ocean to warm up fully in response to increases in greenhouse gases. As a result, ocean warming will continue even if we stop adding greenhouse gases to the atmosphere. Similarly, it can take a long time for glaciers and ice sheets to responds to changes in temperature.

These two factors mean that global sea level will continue to rise for hundreds, if not thousands of years. Exactly how much sea level rise there will be globally is uncertain, but it depends on the amount of greenhouse gases we emit.

CWR: Clearly sea level rise impacts are dire. How will this impact coastal cities in Asia?

Dr. JK: Sea-level rise will bring cascading and compounding impacts in coastal areas. Impacts depend on three things: hazard, exposure, and vulnerability. Many coastal cities are exposed to hazards associated with sea level rise like permanent submergence of areas, flooding, and higher extreme water levels such as those associated with storm surges.

SLR will bring cascading impacts in coastal areas…

…however these impacts depend on how much SLR there is + the adaptation measures in place

There are also potential compound effects which could exacerbate these hazards such as higher intensity tropical cyclones and increases in extreme rainfall associated with climate change. Cities can also be affected by sea level rise via changes in coastal erosion, changes in coastal ecosystems – including things like mangrove forests that can protect coastlines – salinization of soils, ground water and surface water, and reduced drainage. How severe those impacts will be depends on how much sea level rise there is and what measures are taken to adapt to those changes.

CWR: What are the report’s key recommendations? And if you had one piece of advice for global leaders, what would it be?

Dr. JK: One thing the report mentions is that only around half of all countries worldwide have adequate multi-hazard early warning systems. The WMO and the global community are intensifying efforts to strengthen early warning systems and climate services to help society be more resilient to extreme weather and climate.

Further readings

More on Latest

«
»
Related Posts