AI Summary. The International Energy Agency's projection for annual carbon dioxide emissions in 2040 has fallen from 50bn tons to 30bn tons, though the world is expected to fall far short of the 1.5°C Paris goal, with warming likely between 2°C and 3°C by 2100. Global energy demand is projected to more than double by 2050.

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Noting that over the past decade global CO2 emissions projected by the IEA have fallen by more than 40%, Bill Gates argues innovation will likely “give us the tools we need to meet the growing demand for energy without increasing carbon emissions.”

Have emissions forecasts improved even as climate goals go unmet?

Core argument: The International Energy Agency has cut its 2040 global carbon dioxide emissions forecast from 50 billion tons, projected a decade ago, to 30 billion tons, and projects 2050 emissions will be lower still.

Ten years ago, the International Energy Agency predicted that by 2040, the world would be emitting 50 billion tons of carbon dioxide every year. Now, just a decade later, the IEA’s forecast has dropped to 30 billion, and it’s projecting that 2050 emissions will be even lower. Even if the world takes only moderate action to curb climate change, the current consensus is that by 2100 the Earth’s average temperature will probably be between 2°C and 3°C higher than it was in 1850. That’s well above the 1.5°C goal that countries committed to at the Paris COP in 2015. In fact, between now and 2040, we are going to fall far short of the world’s climate goals. One reason is that the world’s demand for energy is going up—more than doubling by 2050. Although wind and solar have gotten cheaper and better, we don’t yet have all the tools we need to meet the growing demand for energy without increasing carbon emissions. But we will have the tools we need if we focus on innovation. With the right investments and policies in place, over the next ten years we will have new affordable zero-carbon technologies ready to roll out at scale. Add in the impact of the tools we already have, and by the middle of this century emissions will be lower and the gap between poor countries and rich countries will be greatly reduced.

Takeaways by Macro Roundup® AI

  1. The International Energy Agency has cut its 2040 global carbon dioxide emissions forecast from 50 billion tons, projected a decade ago, to 30 billion tons, and projects 2050 emissions will be lower still.
  2. The current consensus holds that even with moderate climate action, Earth's average temperature in 2100 will probably be 2–3°C above 1850 levels, well above the 1.5°C goal countries committed to at the 2015 Paris COP.
  3. Global energy demand is set to more than double by 2050, and despite wind and solar becoming cheaper and better, the tools to meet that demand without increasing carbon emissions do not yet all exist.

AI Summary. China has passed the European Union to become the second-largest source of cumulative historical greenhouse gas emissions, behind the United States. Projections based on the International Energy Agency's "stated policies scenario," which tracks nations' current climate actions, show China may nearly catch up with the US.

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China’s cumulative carbon emissions since 1850 have outpaced Europe’s but are still 60% of the US’s level. China has been the world’s #1 carbon emitter since 2006.

Is China now the second-largest source of historical emissions?

Core argument: China has passed the European Union's 27 current member states to become the world's second-largest source of cumulative greenhouse gas emissions.

The United States has burned more fossil fuels than anywhere else in history. Europe has long ranked No. 2 in total historical greenhouse gas emissions. Until now. And projections show that China may nearly catch up with the United States. Data for carbon dioxide-equivalent emissions from 1850 to 2023 is from Jones et al (2024); data for 2024 from Carbon Brief; projected data for 2025 to 2100 is based on the International Energy Agency’s “stated policies scenario” tracking nations’ climate actions. European Union totals were calculated for the current 27 member countries. Lines show cumulative territorial CO2 emissions from fossil fuels, cement, land use, land use change and forestry.

Takeaways by Macro Roundup® AI

  1. China has passed the European Union's 27 current member states to become the world's second-largest source of cumulative greenhouse gas emissions.
  2. Projections based on the International Energy Agency's "stated policies scenario" show China may nearly catch up with the United States, which has burned more fossil fuels than anywhere else in history.
  3. The emissions series combines carbon dioxide-equivalent data from Jones et al (2024) for 1850–2023, Carbon Brief for 2024, and IEA-based projections for 2025–2100, covering fossil fuels, cement, and land use, land use change and forestry.

AI Summary. Economic models have overestimated adoption of carbon capture and storage while underestimating cost declines in solar panels and lithium batteries. Researchers modelling solar, wind, batteries and hydrogen electrolysers under "Wright's law" — where each doubling of production cuts unit costs by a fixed percentage — estimate emissions fall fast enough to meet the 1.5°C target at minimal cost.

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Limiting global warming to the 2° target might be more affordable than projected due to slower economic growth and the ongoing decline in the cost of solar power, wind power, and lithium batteries as production volumes increase.

Will falling clean energy costs make cutting emissions far cheaper?

Core argument: Rupert Way of the University of Cambridge and co-authors model an energy system in which solar power, wind power, lithium battery and hydrogen electrolyser costs follow "Wright's law," a scenario in which emissions fall fast enough to meet the 1.5°C target at minimal cost.

Economic modellers also have a poor record of predicting technological advances. They overestimate the take-up of some technologies (such as carbon capture and storage, whereby carbon dioxide is sucked out of the smokestacks of power stations and factories and stashed away safely underground) and severely underestimate the falling costs of others, most notably solar panels and lithium batteries. Rupert Way of the University of Cambridge and others have modelled an energy system in which the cost of solar power, wind power, lithium batteries and hydrogen electrolysers falls according to “Wright’s law”. This holds that every doubling of production sees unit costs fall by a fixed percentage, with that percentage derived from past experience. In this scenario emissions fall so rapidly that even the 1.5°C target can be met at minimal cost.

Takeaways by Macro Roundup® AI

  1. Rupert Way of the University of Cambridge and co-authors model an energy system in which solar power, wind power, lithium battery and hydrogen electrolyser costs follow "Wright's law," a scenario in which emissions fall fast enough to meet the 1.5°C target at minimal cost.
  2. Wright's law holds that every doubling of production cuts unit costs by a fixed percentage, with that percentage derived from past experience.
  3. Economic modellers have overestimated take-up of carbon capture and storage while severely underestimating the falling costs of solar panels and lithium batteries.

AI Summary. Downward revisions to global population and GDP projections make climate change appear more tractable, the author argues, since the scenarios used to model emissions rely on socio-economic assumptions that are more extreme than real-world observations. With slower population and economic growth, even partial policy successes could bring emissions consistent with a 2C target within reach.

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.@RogerPielkeJr argues that more realistic projections of global population and GDP growth suggest that “even partial future policy successes could more easily bring into view future emissions consistent with a 2C temperature target.”

Do lower population and GDP projections make climate change more tractable?

Core argument: Downward revisions to global population and GDP projections make the challenge of climate change appear more tractable, according to the author, who argues the "assumption space" behind emissions scenarios should shift away from extreme socio-economic assumptions toward scenarios consistent with real-world observations.

Updated understandings of population and GDP suggest that, at a minimum, the “assumption space” used to generate scenarios needs to reorient away from extreme socio-economic assumptions and towards more realistic socio-economic scenarios consistent with observations of the real world. Every time global population GDP projections are revised down, the challenge of climate change appears that much more tractable. Of course, peak population and slower economic growth bring with them considerable societal and policy challenges of their own. “Current policy” projections are based on a very conservative set of assumptions — who thinks there will be no new climate and energy policies? — and many countries have committed to accelerating decarbonization. Conditional on slower-than-projected population and/or GDP growth, that means that even partial future policy successes could more easily bring into view future emissions consistent with a 2C temperature target. Basing our expectations on the latest understandings of population and GDP changes is thus essential for a clear-eyed view of climate and energy challenges.

Takeaways by Macro Roundup® AI

  1. Downward revisions to global population and GDP projections make the challenge of climate change appear more tractable, according to the author, who argues the "assumption space" behind emissions scenarios should shift away from extreme socio-economic assumptions toward scenarios consistent with real-world observations.
  2. "Current policy" emissions projections rest on the conservative assumption that no new climate and energy policies will be adopted, even though many countries have committed to accelerating decarbonization.
  3. Conditional on slower-than-projected population and GDP growth, even partial future policy successes could more easily bring future emissions consistent with a 2C temperature target into view, though peak population and slower growth carry their own societal and policy challenges.

AI Summary. The world's oceans have absorbed 90% of excess heat and about a quarter of human-caused carbon dioxide emissions during the industrial era, and scientists are investigating what drove an anomalous rise in sea temperatures and whether seas will cool again. Researchers caution there is no guarantee oceans will keep absorbing heat at the same rate.

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Oceans have absorbed 90% of the heat from human-caused carbon dioxide emitted during the industrial era, but some scientists are concerned that oceans may be reaching their limits in protecting the planet against the worst extremes of climate change.

Will the oceans keep absorbing most of the world's excess heat?

Core argument: The world's oceans have absorbed 90% of excess heat and about a quarter of human-caused carbon dioxide emitted during the industrial era, heat that did not go into the land surface, atmosphere or ice caps.

Scientists are now trying to understand what has driven the rapid anomalous rise in sea temperatures, why that heat has lingered and whether the world’s seas will cool again. At the heart of these questions is a concern that the oceans may be reaching their limits in the vital role they play in protecting the planet against the worst extremes of climate change. They have absorbed 90% of excess heat and about a quarter of human-caused carbon dioxide emitted during the industrial era. “All that heat that’s going into the ocean is not going into the land surface or into the atmosphere, or into the ice caps,” says Michael Meredith, oceanographer and science leader at the British Antarctic Survey. “The ocean has been doing this huge climate favour for us for decades.” But he adds there is no guarantee it will continue doing so at the same rate. “If this does slow in future, the consequences will be like we saw in 2023 [the hottest year on record] but much more so.”

Takeaways by Macro Roundup® AI

  1. The world's oceans have absorbed 90% of excess heat and about a quarter of human-caused carbon dioxide emitted during the industrial era, heat that did not go into the land surface, atmosphere or ice caps.
  2. Scientists are investigating what drove the rapid anomalous rise in sea temperatures, why that heat has lingered and whether the seas will cool again, amid concern that the oceans may be reaching the limits of their protective role.

AI Summary. Fuel regulations that abruptly cut sulfur dioxide emissions from international shipping by about 80% created an inadvertent geoengineering termination shock, and the authors estimate the resulting radiative forcing over the global ocean could double or more the rate of warming in the 2020s relative to the rate since 1980.

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A 2020 mandate that reduced the emission of sulfur dioxide from international shipping by about 80% likely doubled the rate of global warming by reducing the amount of light being reflected back into space.

Does cutting shipping sulfur emissions accelerate global warming?

Core argument: The 2020 fuel regulations cut sulfur dioxide emissions from international shipping by about 80%, which the authors characterize as an inadvertent geoengineering termination shock with global impact.

In 2020, fuel regulations abruptly reduced the emission of sulfur dioxide from international shipping by about 80% and created an inadvertent geoengineering termination shock with global impact. Here we estimate the regulation leads to a radiative forcing of Wm−2 averaged over the global ocean. The amount of radiative forcing could lead to a doubling (or more) of the warming rate in the 2020s compared with the rate since 1980 with strong spatiotemporal heterogeneity. The warming effect is consistent with the recent observed strong warming in 2023 and expected to make the 2020s anomalously warm. The forcing is equivalent in magnitude to 80% of the measured increase in planetary heat uptake since 2020. The radiative forcing also has strong hemispheric contrast, which has important implications for precipitation pattern changes.

Takeaways by Macro Roundup® AI

  1. The 2020 fuel regulations cut sulfur dioxide emissions from international shipping by about 80%, which the authors characterize as an inadvertent geoengineering termination shock with global impact.
  2. The authors estimate the resulting radiative forcing over the global ocean could lead to a doubling or more of the warming rate in the 2020s relative to the rate since 1980, with strong spatiotemporal heterogeneity.
  3. The estimated forcing is equivalent in magnitude to 80% of the measured increase in planetary heat uptake since 2020 and is consistent with the strong warming observed in 2023.

AI Summary. The National Climate Assessment estimates that a 9°F rise in global average temperatures would reduce U.S. gross domestic product in 2090 by 4%, plus or minus 2%, relative to a world without human influence on the climate. The Intergovernmental Panel on Climate Change puts a 5°F rise at roughly 3% of global output in 2100.

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According to the Intergovernmental Panel on Climate Change a global temperature rise of 5°F would reduce annual GDP growth by 0.05 percentage point.

According to the Intergovernmental Panel on Climate Change a global temperature rise of 5°F would reduce annual GDP growth...

How large is the projected economic cost of rising temperatures?

Core argument: The National Climate Assessment's final chapter estimates that a 9°F rise in global average temperatures, beyond the 1.4°F recorded since 1880, would reduce U.S. GDP in 2090 by 4% plus or minus 2% relative to a no-human-influence baseline.

The National Climate Assessment's numbers, uncertain as they are, turn out not to be all that alarming. The final figure of the final chapter shows that an increase in global average temperatures of 9 degrees Fahrenheit (beyond the 1.4-degree rise already recorded since 1880) would directly reduce the U.S. gross domestic product in 2090 by 4%, plus or minus 2%—that is, the GDP would be about 4% less than it would have been absent human influences on the climate. That “worst-worst case” estimate assumes the largest plausible temperature rise and only known modes of adaptation. Buried in the Intergovernmental Panel on Climate Change’s 2014 report is a chart showing that a global temperature rise of 5 degrees Fahrenheit would have a global economic impact of about 3% in 2100—negligibly diminishing projected global growth over that period to 385% from 400%. To put it another way, the projected reduction in the average annual growth rate is a mere 0.05 percentage point. The U.S. economy in 2090 would be no more than two years behind where it would have been absent man-caused climate change.

Takeaways by Macro Roundup® AI

  1. The National Climate Assessment's final chapter estimates that a 9°F rise in global average temperatures, beyond the 1.4°F recorded since 1880, would reduce U.S. GDP in 2090 by 4% plus or minus 2% relative to a no-human-influence baseline.
  2. That 4% figure is a "worst-worst case" assuming the largest plausible temperature rise and only known modes of adaptation, leaving the U.S. economy in 2090 no more than two years behind where it would otherwise have been.
  3. A chart in the Intergovernmental Panel on Climate Change's 2014 report shows a 5°F global temperature rise producing a global economic impact of about 3% in 2100, trimming projected growth to 385% from 400%—0.05 percentage point off average annual growth.