A dangerous yet persistent myth is that climate change is a slow-rolling issue. We see this idea play out in our collective climate response, which has historically focused on end-of-century timeframes. In reality, at about 1.1°C of current warming, we’ve already observed stronger and more frequent extreme weather events like wildfires, droughts, precipitation, and heat waves. Additionally, species are migrating towards higher latitudes or elevations as some areas become uninhabitable, extinctions are being linked directly to climate change, widespread coral bleaching and loss of ocean biodiversity are occuring, food security is declining as crop yields and fisheries suffer, and water scarcity is expanding.1
Unfortunately, even on the most aggressive mitigation (greenhouse gas emission reduction) pathways, we’ll see additional warming this century, exacerbating all of these effects. The question is, how much more warming (and how fast?) will we cause before we reverse direction and start cooling? The lower the eventual peak temperature, and slower we get there, the better.
How we manage near-term warming—the temperature progression over the next few decades—determines not just the warming we feel today, but also how we stabilize long-term temperatures.2 Because climate change is caused by multiple greenhouse gases, each with different warming and lifetime dynamics, a sole focus on long-term warming (driven largely by carbon dioxide (CO₂)) can put near-term warming (heavily influenced by short-lived climate pollutants like methane (CH₄)) more at risk, and vice versa. The short-lived climate pollutants that drive near-term warming are contributing the majority of current warming, and cannot be ignored. Because of their short-lived nature, cutting them also provides an opportunity to start reversing temperature when paired with hitting net zero carbon dioxide emissions. We need to work on both long- and near-term warming.
Our only chance at staying below 1.5°C, the warming threshold outlined in the 2015 Paris Agreement, is to successfully and aggressively address near-term and long-term warming in parallel.3 Overshooting the 1.5°C warming threshold in the near-term would likely lead to irreversible damage, even if temperatures drop again by 2100. When compared to a world where warming remains below 1.5°C, overshooting this threshold could mean losing 70-90% of reef-building corals,4 5 committing ourselves to tens of centimeters of additional sea level rise6 7 or more,8 triggering tipping points with critical thresholds between 1.5°C and 2°C (e.g. coral reefs, alpine glaciers, Arctic summer sea ice, Greenland ice sheet and West Antarctic ice sheet),9 and sacrificing global GDP growth over the long-term far in excess of the cost of upfront mitigation to say within 1.5°C.10
Near-term warming has historically been overlooked as the worst impacts of climate change were viewed as far into the future. That’s less true now—while we certainly haven’t yet hit peak warming, there’s heightened awareness of increasingly harmful climate impacts today, in sometimes irreversible ways. Near-term warming poses a number of significant environmental and social risks that could greatly increase global human suffering, and at the same time, hurt our chances of reaching long-term climate goals like keeping global warming within 1.5˚C. Each uptick of warming puts more people and ecosystems at risk,11 making it critical that we minimize warming as much as possible every step along the way, not just by 2100.
Not all emissions pathways are created equal
Emissions trajectories are considered ‘1.5°C compatible’ if they are likely to result in global temperatures increases of less than 1.5°C by 2100.12 However, many of these pathways actually exceed 1.5°C warming in the near-term, around mid-century, before dropping back down.
Source: IPCC 2018, p. 62
This overshoot shouldn’t be ignored—every additional fraction of a degree increases the risk of environmental destabilization as well as societal destabilization. These dangers are both interconnected and compounding;6 the most fragile ecosystems and vulnerable communities will be most impacted, with ramifications that could cascade globally.
Near-term warming risks environmental destabilization
Near-term warming impacts ecosystems in two key ways: 1) ecosystems struggle to adapt to the rapid rate of warming, and 2) high temperatures raise the risk of accelerating climate feedbacks and triggering non-linear tipping points.
Tenths of a degree can mean the difference between a healthy ecosystem and one facing collapse. Our current level of warming (~1.1°C) has already pushed many ecosystems to the edge, with cascading downstream effects, including acidifying and warming oceans resulting in coral bleaching that impacts ocean biodiversity and human food security, drought-triggered wildfires that spread desertification, threaten ancient redwood trees, cause severe air pollution and release greenhouse gases, and sea ice loss that leads some Arctic predators to starve while further amplifying warming.
Any additional warming, even if we stay within the 1.5°C limit, will also have severe and dangerous consequences since climate impacts compound superlinearly.13 Each fraction of a degree increases the risk of extreme weather events like hurricanes, droughts, and heatwaves, as well as the risk that multiple events will occur in the same region or within a short period of time, multiplying their human and environmental impact.14
In addition to the impact of high temperatures themselves, the rate of warming is associated with a distinct set of risks that determine how (or whether) ecosystems adapt to the changing conditions.
The current rate of warming is unprecedented within at least the last 2000 years,15 16 if not much longer.17 18 Our impact on the climate is so unprecedented that some scientists now say that we have entered a new geologic era—one that they are calling ‘the anthropocene’. In this new era of human-driven warming, some species are simply unable to adapt rapidly enough to keep pace,19 20 leading to what some scientists are calling the sixth mass extinction—the first one in 65 million years.21
Temperature changes over the past 2000 years relative to the global mean temperature between 1850 and 1900. The gray bar on the left axis represents the estimated temperature range during the warmest multi-century period in the last 100,000 years. Source: IPCC 2021 SPM, p. 6.
Climate feedback loops and tipping points
Ecosystems are constantly adjusting and readjusting to changing conditions. Typically, a healthy ecosystem is resilient enough to be able to bounce back after a disturbance, or to adjust to gradual changes. Significant and rapid warming can destabilize that balance, contributing to climate feedbacks and triggering tipping points.
Elevated temperatures steadily increase the risk of positive feedback loops, which are natural processes that are both driven by warming and further amplify warming. For example, the ‘ice-albedo feedback’ is a process in which the planet becomes less reflective (lowered albedo) because highly reflective ice is being replaced by dark water as the ice melts. This leads to less solar radiation being reflected back into outer space and more heat being absorbed on Earth, which worsens warming.
While feedback impacts increase more gradually with warming, tipping points, such as the shutting down of ocean circulation in the North Atlantic and loss of continental ice sheets, are characterized by abrupt, non-linear, and sometimes irreversible change. Tipping points are often preceded by more gradual, lower-impact natural feedbacks, and the classification between the two can be fluid as the science around them evolves.
Managing near-term warming is critical because there are both climate feedbacks and tipping points that could be triggered by small additional increases in temperature, given how much warming we’ve already caused. Already, positive feedbacks have increased the amount of warming we experience, and evidence suggests that many tipping points, including the Amazon forest dieback,22 permafrost thaw,23 and Arctic sea ice loss, are on the verge of being triggered.24
Table 1. Selected Earth system tipping points and their estimated tipping ranges, adapted from Lenton et al. 2008, Steffen et al. 2018, and IPCC 2021
|Tipping Element||Estimated Tipping Range*||Transition Timescale||Key Impacts|
|Arctic summer sea ice||~1-3°C||Decadal||Amplified warming, ecosystem change|
|Greenland ice sheet loss||~1-3°C||Centuries to millennia||Sea level +2–7 m|
|West Antarctic ice sheet loss||~1-3°C||Centuries to millennia||Sea level +5 m|
|Coral reef bleaching||~1-3°C||~1 year||Biodiversity loss, threats to food security|
|Indian summer monsoon||~3-5°C||~1 year||Drought|
|Atlantic thermohaline circulation||~3-5°C||Centuries||Regional cooling, sea level, ITCZ shift|
|Tropical forest dieback||~3-5°C||Multi-decadal||Biodiversity loss, decreased rainfall|
|Boreal forest dieback||~3-5°C||Multi-decadal||Biome switch|
|Permafrost||**||Multi-decadal||CH₄ and CO₂ release|
|Marine methane hydrates||~2-6.5°C||Multi-millennium||CH₄ release|
*Estimated tipping range refers to the range of global average surface temperature increase that could lead these systems to tip. Note that there is still significant uncertainty surrounding these values, and some tipping points can be triggered by a combination of warming and other factors. For example, deforestation and drought in the Amazon could push the system toward a tipping point more rapidly than warming alone.22
**Permafrost thaw is already occurring, but there is uncertainty surrounding whether the system is likely to continue to respond linearly or tip into a new state. Some propose that the system would tip at 5°C or more,25 while others have suggested that we have already passed a permafrost tipping point.23
To make matters worse, research shows that we may be underestimating the impact that many feedbacks and tipping points would have on climate stability. Some feedbacks, including wetland methane emissions, might contribute more additional warming than previously believed,26 and some systems, including ocean circulation and coral reefs,27 may ‘tip’ into new states at temperatures that were previously considered ‘safe’ (e.g. between 1.5 and 2°C above pre-industrial).28 29 There are also still big areas of uncertainty in our current scientific understanding of natural feedbacks, including how much these feedbacks are expected to contribute to additional warming.30 Adequately managing the risk they pose to environmental stabilization increases the chance we avoid near-term temperature spikes that could thwart our progress towards long-term climate stability.
Natural Disasters and Resource Stress
Any additional warming in the near-term could have huge, negative, destabilizing effects on economies, food systems and societies themselves.31 Already, the frequency and intensity of extreme weather events and natural disasters, such as droughts, floods, hurricanes, and heat waves, have increased. As temperatures continue to rise toward 1.5°C and beyond, the magnitude of these impacts will also continue to climb, increasing in severity and the number of people affected.31 Beyond the acute impacts of specific events, extreme weather events can have prolonged effects as croplands lose viability, yields suffer, food insecurity rises, and people are displaced from their homes and countries.28
All of these effects risk furthering societal instabilities, which among other harms, could also further threaten our chances of meeting longer-term climate goals. A society consumed with worrying about access to food, shelter, clean water, and extreme weather impacts, is unlikely to prioritize global collaboration or infrastructure overhaul to reach long-term climate stability.
Global justice and social stability
While climate change has global impacts, its effects are unevenly distributed, and are often compounded by factors such as geography, socio-economic status, land use patterns, and the relative strength of a given region’s economy and government. As one example, it is estimated that it will take double the amount of global mean warming for wealthy countries to experience the same relative changes in extreme heat as lower-income countries, many of which are found in the equatorial belt.32 Between 3.3 and 3.6 billion people are considered highly vulnerable to climate change, partially due to their dependence on at-risk ecosystems.33
Many communities, particularly those in the Global South, small island nations, and others whose social, economic, or geographic position makes them vulnerable to climate change are the ones feeling the worst effects,34 35 despite not significantly contributing to the problem nor benefiting as significantly from historic fossil fuel-powered economic development. This is deeply unjust, as well as being a serious risk factor in an effective climate response. Not taking these communities’ needs into account in our collective climate response risks worsening inequalities that destabilize parts of society, and the very economic and political engine required to drive a rapid response.
In order to maximize the chance of success of our collective climate response, it is essential that marginalized voices are part of decision-making going forward. Given the lack of this inclusion in the past, it is no surprise that many marginalized communities are deeply skeptical of vague assurances of ‘net-zero by mid-century’ or long-term temperature targets, particularly given industrialized countries’ lack of sufficient progress so far.
If we fail to aggressively address near-term warming, the combination of accelerating climate impacts, and the eventual public realization that known climate action strategies to manage near-term warming were left on the table could erode the public’s trust in critical institutions, hampering their ability to operate effectively and causing political blowback.
In the United States, President Biden campaigned with promises to fight climate change and make it one of his administration’s top priorities. After over a year in office and few successful climate policies passed, many of his original supporters are losing trust in his ability to deliver on his promises. If the public loses faith in the ability of pro-climate-action leaders to take effective action, their support, and therefore ability to act, may erode further.
This danger is not unique to the United States. Since social trust in political institutions is critical to effectively address grand social challenges like climate change,36 37 any perception that governments and institutions are not performing adequately and promptly can further erode public trust, and hamper future climate action.36
Unabated near-term warming poses a number of threats to environmental and social stability that could impact our collective ability to stay within long-term warming guardrails. While increasing efforts on our long-term temperature trajectories, we also need to simultaneously work to reduce warming in the near-term, within this generation. We must learn to walk and chew gum at the same time—the social and economic benefits to society are massive.
The critical need to address near-term warming is hindered by a sole focus on long-term temperature targets and CO₂ emissions reductions in most narratives, as opposed to a more expansive approach to aggressively mitigating all greenhouse gases.
The following blog post in this series will examine a concept called ‘Radiative Forcing’ that is fundamental for understanding and guiding our response to near-term warming.
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