Report shows 2023 marked by record-breaking greenhouse gas levels, extreme heat and high sea levels

Last year was another record year for carbon pollution, global temperatures, sea level rise and natural disasters, according to the latest international report on the world's climate published Thursday.

More than a dozen CU Boulder researchers contributed to the 34th annual State of the Climate report, led by scientists from the National Oceanic and Atmospheric Administration.

According to the report, the concentrations of Earth's main greenhouse gases-carbon dioxide, methane and nitrous oxide-reached record highs last year. The increase from 2022 was one of the highest on record despite global commitments to cut emissions.

"We are definitely not on the right path to limit global warming," said Xin Lindsay Lan, the report's co-author and a researcher at the Cooperative Institute for Research in Environmental Sciences (CIRES) at CU Boulder. "The planet is already warming rapidly, so it's a critical time to reduce those greenhouse gas levels in the atmosphere. Instead, we are seeing a rapid increase."

The report, published in the Bulletin of the American Meteorological Society, also revealed that 2023 was the hottest year on record. Global mean sea level reached a record high for the 12th consecutive year. Heatwaves, storms and droughts also plagued the planet, while catastrophic wildfires pumped more emissions into the atmosphere.

CU Boulder Today sat down with Lan, who led the reporting of global greenhouse gas levels, to discuss the importance of emission reduction.

What do you make of the fact that emissions are still increasing?

It is very concerning, because we are already at pretty high levels of global warming. The global average warming in the last decade is about 1.1°C above pre-industrial levels. Climate scientists like me are concerned that if global warming exceeds 1.5 °C, we could be facing some severe climate crises. So it's very important that we try our best to limit greenhouse gas emissions and avoid crossing that threshold.

Many countries and entities have committed to cutting emissions. Are these efforts working?

Although there have been many efforts to cut emissions globally, our data shows that global greenhouse gas concentrations remain at very high levels. If emissions had decreased significantly, we would have seen a slowdown in the rise of global CO₂ levels, but there's no evidence of that. In fact, the increase in CO₂ from 2022 to 2023 was the fourth largest in recorded history.

Many countries pledged to reach net zero emission by around 2050, so we may see the global CO₂ emissions continue to increase at a fast pace until then.

Why is so much climate discussion focused on CO₂?

CO₂ is the most important greenhouse gas, and the main source of global carbon emissions is fossil fuel use. It contributes to about 66% of the global radiative energy increase, which directly leads to global warming.

While methane has a greater warming power than CO₂ per molecule, it has a shorter lifespan in the atmosphere after it's released. When CO₂ is emitted, it can stay in the air for thousands of years, and it will continue to trap heat. A lot of the CO₂ in the air now has been there since the industrial era. Even if we stop emitting CO₂ today, we will continue to see warming effects from the CO₂ we've been putting into the air.

In 2023 wildfires in Canada spewed 3 billion tons of CO₂-the equivalent of emissions from 647 million cars in a year. Did natural disasters contribute to the record high emissions?

The fires certainly contributed to our emissions last year. In addition to the fires and burning of fossil fuels, 2023 was a year of El Niño, which is a climate pattern characterized by warmer than normal ocean temperatures that release large amounts of heat into the atmosphere.

In warm years like 2023, a lot of forests may be under stress, which would reduce their CO₂ uptake. A warmer ocean may also absorb less CO₂ than normal.

What can society do?

One critical thing that we need is global collaboration. Greenhouse gasses, given their long lifespans in the atmosphere, do not respect state boundaries. We need to work together as a global community to reduce global greenhouse gas emissions.

What can individuals do?

It's important for individuals to believe they can make a difference in changing the course of climate change. One of the most critical things we can do is to limit our energy use, because the energy sector is the biggest source of greenhouse gas emissions. We can try to use renewable energy for our commutes to work. We can try to take public transportation when possible. We can reduce methane emissions by limiting food waste that goes to the landfill.

In addition to reducing our own carbon footprints, I would encourage individuals to vote and talk to your representative about your concerns on global warming.

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