One decade ago, the world was on pace to warm by nearly 4°C (7.2°F) above pre-industrial levels by the end of the century, a scenario likely to usher in devastating impacts including inundation of coastal cities, severe disruptions to food production, unprecedented heatwaves, exacerbated water scarcity, a spike in high-intensity tropical cyclones, and irreversible loss of biodiversity.
Now, things don’t look quite as bad.
“When countries came together in 2015, to negotiate the Paris Agreement, global greenhouse gas emissions were rising with really no end in sight,” said Taryn Fransen, Director of Science, Research, and Data for World Resources Institute’s (WRI) Global Climate Program, at a WRI webinar on Tuesday. “Over the past decade, this picture has changed more dramatically than we sometimes realize — thanks in part to the commitments that countries made under Paris.”
Dramatically indeed. Per Climate Action Tracker, current policies presently in place project to result in about 2.7°C (4.9°F) of warming — an improvement of over a degree.
“Emissions are now projected to be lower in 2030 than they were in 2015,” Fransen added.
Nationally Determined Contributions
Fransen attributes much of this success to the Nationally Determined Contributions (NDCs), or climate action plans which each signatory of the Paris Agreement must establish and revise every five years. NDCs set goals for mitigating greenhouse gas emissions, determine how to achieve the goals, create monitoring and accountability mechanisms, and make financing plans.
“This really reflects, I think, the efforts that countries have made over the last decade to strengthen their [NDC] commitments,” said Fransen of the world’s improved warming trajectory.
Signed by 195 countries in 2015, the Paris Agreement is an international treaty aiming to keep global warming to under 2°C (3.6°F) above pre-industrial times by 2100, and ideally under 1.5°C (2.7°F). Though today’s NDCs are not in line with this goal, they did highlight the potential for these documents to generate tangible progress.
“We still have a long way to go to close the gap between countries’ policies and their targets. And moreover, between the targets that they've set and the 1.5 degree goal,” said Fransen. “This next round of NDCs provides an opportunity to align near and midterm targets with these very ambitious long term goals.”
NDC revisions have boosted ambition before. During the most recent round of updates in 2020-2021, Morocco added nine new climate mitigation actions, Vietnam projected 34% greater emissions reductions, and Jamaica committed a 60% increase in its emissions cuts target — to name just a few.
Fending Off Tipping Points
While far from sufficient in meeting the Paris Agreement target and avoiding devastating future climate impacts, the reduction in projected warming to date is significant. A 2022 Science study examined sixteen critical climate “tipping points,” or natural thresholds that, when crossed, lead to large, self-perpetuating, irreversible changes in the climate system.
The authors found fourteen of the tipping points would likely be crossed at 4°C of warming. But at 2.7°C of warming — which today’s policies would cause — the world would only cross seven.
In other words, under current policies, seven of the most catastrophic climate scenarios have now been successfully averted:
1. West African monsoon shift
When the surface temperatures of arid West Africa heat up during the summer, they create an area of low pressure, drawing the relatively cool moist winds from the Atlantic Ocean that bring the region’s wet season. As climate change drives surface temperatures even warmer, this system intensifies, which could have prompted a tipping point where regions like the Sahara Desert could have suddenly supported vegetation — which would have led to more evapotranspiration, more precipitation, etc.
While desirable in some aspects for the Sahara to bloom, scientists worried that more extreme rains could have caused flooding and severe storms in these parts of West Africa, while other neighboring regions could have gotten drier as a result. Furthermore, dusty winds from West Africa play a role in disrupting the formation of Atlantic hurricanes, so losing this dusty air could have spurred worse storms in the Americas.
The authors find an abrupt greening and wetting scenario at 2.8°C of warming, which has now been averted.
2. East Antarctic glacier collapse
With much of the East Antarctic ice sheet resting on bedrock far above sea level, East Antarctica is far more stable than West Antarctica and Greenland — which are already nearing critical tipping points. However, at 3°C of warming, the authors find the collapse of East Antarctica’s floating ice shelves, which could have led several subglacial basins to retreat.
Ice reflects sunlight, so as it melts, the Earth begins absorbing more sunlight leading to an increased warming effect. Land ice entering the ocean can cause dramatic sea level rise, destroying ecosystems and inundating coastal cities.
While sea level rise and glacier collapse remain issues, this particular tipping point has now been warded off.
3. Amazon rainforest dieback
In the 1970s, the Amazon rainforest generated half of its own rainfall, as the water stored in its soil and leaves evaporated and reentered the atmosphere. But when atmospheric carbon dioxide rises, pores in plant leaves open less widely, reducing that evapotranspiration.
With more extreme global warming, this phenomenon — coupled with changing sea surface temperatures and the potential for continued deforestation in the Amazon — could have pushed the Amazon to a tipping point where it would not have enough rain to support itself, leading to a mass dieback and transition to savannah-like conditions. This scenario would have prompted socioeconomic damage in the trillions, an ecological catastrophe for the Amazon’s unique wildlife, and the release of carbon dioxide previously stored by the rainforest, further exacerbating climate change.
The authors estimate this tipping point at 3.5°C, which has now been avoided.
4. Northern permafrost collapse
Permafrost describes the thick ice-filled layer of soil found in cold regions that stays below freezing year round. Over millennia, the permafrost has trapped over a trillion tons of carbon derived from dead plants and animals — around twice as much carbon as is currently in the Earth’s atmosphere.
Climate change is already contributing to the thaw of permafrost, and subsequent release of stored carbon. In fact, northern permafrost is already nearing a first critical tipping point whereby released carbon contributes to more warming which thaws more permafrost.
However, the authors warned of a second tipping point called the “compost bomb instability,” where warmer soil temperatures would increase underground microbial activity, and the soil would start generating heat of its own. In this worst case scenario, even a stop to global warming would not be able to halt permafrost collapse. The authors estimate this tipping point at 4°C.
5. Atlantic meridional overturning circulation (AMOC) collapse
AMOC is an important Atlantic Ocean current that, among other things, brings warmth and nutrients to the Northern Hemisphere. AMOC became the subject of several news stories last summer, as news outlets including New York Post, LiveScience, and The Guardian published stories with headlines mistakenly claiming the Gulf Stream could collapse as soon as 2025.
Though the Gulf Stream and AMOC are different currents and AMOC’s collapse is not imminent according to most experts, AMOC is weakening. AMOC is powered in part by salty surface water sinking in the North Atlantic, and due to the melt of the Greenland ice sheet, the North Atlantic is becoming saturated with freshwater. If AMOC were to collapse, Europe could see temperatures plummet and weather systems across the planet could turn more extreme.
Though some scientists fear this tipping point could come sooner, the authors of the Science study put this tipping point at 4°C.
6. Northern forest dieback
Many forests are resilient to one or two stresses, but can’t handle a death by a thousand cuts. That’s what a 4°C world would have meant for boreal forests, which account for 30% of the world’s forests and store over a third of all terrestrial carbon. A warmer climate brings disease, pests, lower reproduction, drought, fire, and more — and if one such incident wipes out a large swath of trees, these new conditions could have made it impossible for the forest to regenerate.
While boreal forests are individually struggling to withstand the impacts of today’s climate change, the warming threshold at which forests can no longer grow will not be crossed.
7. Northern forest expansion
On the flip side, the northern edge of boreal forests has begun encroaching into the tundra. As previously mentioned, ice reflects sunlight, so replacing tundra with forest would cause the Earth to absorb more sunlight, leading to more warming. But the authors put this tipping point at 4°C as well, meaning this tipping point is no longer an issue.
Challenges Ahead
While the NDCs helped shift a decade of global policy to avert these seven critical tipping points, there are still seven remaining — four of which are projected to occur at 1.5°C of warming. That’s why, at the WRI panel, experts acknowledged the effectiveness of the NDC process while advocating for significantly more ambitious plans going forward.
"While we have made important progress since 2015, the progress is really incremental relative to the transformative change that needs to occur,” said Fransen.
In mapping out strategies to achieve that transformative change, panelists discussed some limitations of NDCs. According to Tomas Anker Christensen, Denmark’s Ambassador for Climate Change, one issue is that NDCs can lead countries to form individual plans in isolation rather than working together.
“We approach this on a national basis, a vertical silo basis, every country on its own,” said Christensen. “But the technologies that we require, in order to scale the transition — they are horizontal. They have to be developed collaboratively. Not one country can do it alone.”
“In a way, the way the NDC forces us to think and organize was contrary to the logic of how we actually generate the most action,” Christensen added.
Along with multilateral collaboration, panelists explained that to ensure a just and comprehensive NDC, countries must make an effort to consult their citizens.
“How do we involve people into developing our NDC? How participatory are those plans?” asked Ana Toni, National Secretary for Climate Change at Brazil’s Ministry of Environment and Climate Change. “Just transition is not something that we can do [without] listening to people.”
At the 2023 United Nations Climate Change Conference (COP28) in the United Arab Emirates, countries performed the first global stocktake, assessing current progress and laying out next steps. While critiqued by many environmentalists for using soft language, COP28’s final agreement called for a just, orderly, and equitable “transition away from fossil fuels” — the first direct mention of the leading contributor to human-caused climate change in a UN agreement.
Though nations’ third revisions of their NDCs aren’t due until 2025, some hope to have theirs submitted in time for COP29, which will take place in Azerbaijan this November. According to Fransen, this next year presents a key opportunity to translate NDC ambitions into further concrete action.
“The NDCs work best when we think of them not as a document or as a target, but as a process,” said Fransen. “We have an opportunity over the next year to really use that process to set countries up to drive action on the ground.”
In Brazil, Toni acknowledged that the process isn’t perfect. But she expressed optimism that through cooperation, continued progress is possible.
“There is no magic bullet for how we are going to go forward, but I think we are all trying our best,” said Toni. “It’s all of us together. Together is a really important part.”
Use the NDC Registry to read your country’s nationally determined contributions.