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Climate warming disproportionately impacts countries in the Global South by increasing extreme heat exposure. However, geographic disparities in adaptation capacity are unclear. Here, we assess global inequality in green spaces, which urban residents critically rely on to mitigate outdoor heat stress. We use remote sensing data to quantify daytime cooling by urban greenery in the warm seasons across the ~500 largest cities globally. We show a striking contrast, with Global South cities having ~70% of the cooling capacity of cities in the Global North (2.5 ± 1.0 °C vs. 3.6 ± 1.7 °C). A similar gap occurs for the cooling adaptation benefits received by an average resident in these cities (2.2 ± 0.9 °C vs. 3.4 ± 1.7 °C). This cooling adaptation inequality is due to discrepancies in green space quantity and quality between cities in the Global North and South, shaped by socioeconomic and natural factors. Our analyses further suggest a vast potential for enhancing cooling adaptation while reducing global inequality. A 1.5-fold gap exists in green space cooling adaptation between cities in the Global South and North. Enhancing urban green space quality and quantity offers vast potential for improving outdoor cooling adaptation and reducing its global inequality.

Potential climate tipping points pose a growing risk for societies, and policy is calling for improved anticipation of them. Satellite remote sensing can play a unique role in identifying and anticipating tipping phenomena across scales. Where satellite records are too short for temporal early warning of tipping points, complementary spatial indicators can leverage the exceptional spatial-temporal coverage of remotely sensed data to detect changing resilience of vulnerable systems. Combining Earth observation with Earth system models can improve process-based understanding of tipping points, their interactions, and potential tipping cascades. Such fine-resolution sensing can support climate tipping point risk management across scales. Climate change could drive critical parts of the Earth system past tipping points, causing large-scale, abrupt and/or irreversible changes that harm societies. Here, the authors suggest that satellite remote sensing can play a unique role in helping manage these profound risks, by providing improved early warning of tipping points across scales.

Non-technical summaryTransforming towards global sustainability requires a dramatic acceleration of social change. Hence, there is growing interest in finding ‘positive tipping points’ at which small interventions can trigger self-reinforcing feedbacks that accelerate systemic change. Examples have recently been seen in power generation and personal transport, but how can we identify positive tipping points that have yet to occur? We synthesise theory and examples to provide initial guidelines for creating enabling conditions, sensing when a system can be positively tipped, who can trigger it, and how they can trigger it. All of us can play a part in triggering positive tipping points.Technical summaryRecent work on positive tipping points towards sustainability has focused on social-technological systems and the agency of policymakers to tip change, whilst earlier work identified social-ecological positive feedbacks triggered by diverse actors. We bring these together to consider positive tipping points across social-technological-ecological systems and the potential for multiple actors and interventions to trigger them. Established theory and examples provide several generic mechanisms for triggering tipping points. From these we identify specific enabling conditions, reinforcing feedbacks, actors and interventions that can contribute to triggering positive tipping points in the adoption of sustainable behaviours and technologies. Actions that can create enabling conditions for positive tipping include targeting smaller populations, altering social network structure, providing relevant information, reducing price, improving performance, desirability and accessibility, and coordinating complementary technologies. Actions that can trigger positive tipping include social, technological and ecological innovations, policy interventions, public investment, private investment, broadcasting public information, and behavioural nudges. Positive tipping points can help counter widespread feelings of disempowerment in the face of global challenges and help unlock ‘paralysis by complexity’. A key research agenda is to consider how different agents and interventions can most effectively work together to create system-wide positive tipping points whilst ensuring a just transformation.Social media summaryWe identify key actors and actions that can enable and trigger positive tipping points towards global sustainability.

Atmospheric greenhouse gas concentration has been steadily increasing since the 19th century, causing global warming. Despite efforts to reduce emissions, current projections anticipate a significant increase in global surface temperature by the end of the century, which may push us beyond a safe and just operating space. We must develop emissions pathways that consider renewable technology innovation, climate policy development and consumer behaviour change. In this manuscript we assess corporate emissions reduction ambition in the context of reduction pathways, and in doing so show that company reporting has reached a scale and quality that it can be used to supplement global emissions forecasting. We find emissions disclosures of target-setting companies to account for roughly 20% of global emissions and 60% of global market capitalisation. Of these, we find near-term targets to be consistent with the aggressive reduction requirements of the divergent net-zero scenario published by the Network for Greening the Financial System, but commitments to 2050 are lacking. There is a large disparity between the total market capitalisation of disclosing companies and the total emissions they cover, a disconnect which we emphasise must be addressed by future policy.

Unsustainable snaring is causing biodiversity declines across tropical protected areas, resulting in species extinctions and jeopardizing the health of forest ecosystems. Here, we used 11 years of ranger‐collected data to assess the impact of intensive snare removal on snaring levels in two protected areas in Viet Nam. Snare removal resulted in significant declines in snare occupancy (36.9, 95% Bayesian credible interval [4.6, 59.0] reduction in percent area occupied), but snaring levels nonetheless remained high (31.4, [23.6, 40.8] percent area occupied), and came with a substantial financial cost. Our results indicate that snare removal remains an important component of efforts to protect tropical protected areas but by itself is likely insufficient to address this threat. To stop snaring in protected areas, a multifaceted approach will be necessary that combines short‐term reactive snare removal with long‐term proactive programs that address the underlying drivers behind snaring.

Keeping the Earth system in a stable and resilient state, to safeguard Earth's life support systems while ensuring that Earth's benefits, risks, and related responsibilities are equitably shared, constitutes the grand challenge for human development in the Anthropocene. Here, we describe a framework that the recently formed Earth Commission will use to define and quantify target ranges for a “safe and just corridor” that meets these goals. Although “safe” and “just” Earth system targets are interrelated, we see safe as primarily referring to a stable Earth system and just targets as being associated with meeting human needs and reducing exposure to risks. To align safe and just dimensions, we propose to address the equity dimensions of each safe target for Earth system regulating systems and processes. The more stringent of the safe or just target ranges then defines the corridor. Identifying levers of social transformation aimed at meeting the safe and just targets and challenges associated with translating the corridor to actors at multiple scales present scope for future work. Plain Language Summary For the first time in human history, we are now forced to consider the real risk of destabilizing our home, planet Earth. This is an existential risk, as we all need a planet that can sustain life and provide the basis for the well‐being of all people. Here, we outline a conceptual framework for a global‐scale “safe and just corridor” that delivers on these goals for people and the planet. The recently formed Earth Commission will use this framework to map key functions that regulate the state of the Earth system and provide life support to us humans, including processes such as biodiversity and nutrient cycling. It will also analyze the related justice components, for each of these Earth system target domains, in terms of how such ranges can be defined and how nature's contributions to people can be justly shared. Furthermore, social transformations that meet safe and just targets for all people and how the global‐scale targets can be translated to targets for actors at other scales will be explored. Key Points An integrated people and planet perspective is required to guide human development and use of the global commons We outline an approach to defining a safe and just corridor for a stable and resilient planet supporting human development A conceptual framework for linking safe and just Earth system targets is proposed

Ongoing global warming induced by anthropogenic emissions has opened the debate as to whether geoengineering is a 'quick fix' option. Here we analyse the intended and unintended effects of one specific geoengineering approach, which is enhanced weathering via the open ocean dissolution of the silicate-containing mineral olivine. This approach would not only reduce atmospheric CO2 and oppose surface ocean acidification, but would also impact on marine biology. If dissolved in the surface ocean, olivine sequesters 0.28 g carbon per g of olivine dissolved, similar to land-based enhanced weathering. Silicic acid input, a byproduct of the olivine dissolution, alters marine biology because silicate is in certain areas the limiting nutrient for diatoms. As a consequence, our model predicts a shift in phytoplankton species composition towards diatoms, altering the biological carbon pumps. Enhanced olivine dissolution, both on land and in the ocean, therefore needs to be considered as ocean fertilization. From dissolution kinetics we calculate that only olivine particles with a grain size of the order of 1 μm sink slowly enough to enable a nearly complete dissolution. The energy consumption for grinding to this small size might reduce the carbon sequestration efficiency by ∼30%.

Due to insufficient emission reductions in recent years, it is increasingly likely that global warming will exceed the 1.5 °C temperature limit in the late 2020s or 2030s. As a result, several Earth system tipping elements could, at least temporarily, have their tipping points surpassed, posing risks of large-scale and profound structural change. Tipping does not always occur immediately upon crossing such a critical threshold. If the length of time the driver is beyond the critical level is short enough, tipping could still be avoided for some slow-responding elements of the climate system. An improved understanding is therefore needed of whether tipping remains avoidable, for which systems, and under what conditions. Here, we review how minimising the magnitude and duration of any temperature overshoot beyond 1.5 °C could decrease tipping risks. Tipping elements with fast response times, such as warm-water coral reefs, are especially vulnerable to overshoot. In contrast, those with slow response times, such as polar ice sheets, may be less sensitive to temporary overshoot. Potential interactions between tipping elements and additional human pressures, such as deforestation in the Amazon or pollution and overfishing of coral reef habitats, may further lower tipping points, narrowing the range of overshoot trajectories that can still avoid it. The vulnerability of many tipping elements, even under shorter overshoot conditions, underscores that global warming must peak below 2 °C above pre-industrial levels, return to below 1.5 °C as quickly as possible (i.e. within this century), and to around 1 °C thereafter to limit tipping point risks.

Many scenarios for limiting global warming to 1.5°C assume planetary‐scale carbon dioxide removal sufficient to exceed anthropogenic emissions, resulting in radiative forcing falling and temperatures stabilizing. However, such removal technology may prove unfeasible for technical, environmental, political, or economic reasons, resulting in continuing greenhouse gas emissions from hard‐to‐mitigate sectors. This may lead to constant concentration scenarios, where net anthropogenic emissions remain non‐zero but small, and are roughly balanced by natural carbon sinks. Such a situation would keep atmospheric radiative forcing roughly constant. Fixed radiative forcing creates an equilibrium “committed” warming, captured in the concept of “equilibrium climate sensitivity.” This scenario is rarely analyzed as a potential extension to transient climate scenarios. Here, we aim to understand the planetary response to such fixed concentration commitments, with an emphasis on assessing the resulting likelihood of exceeding temperature thresholds that trigger climate tipping points. We explore transients followed by respective equilibrium committed warming initiated under low to high emission scenarios. We find that the likelihood of crossing the 1.5°C threshold and the 2.0°C threshold is 83% and 55%, respectively, if today's radiative forcing is maintained until achieving equilibrium global warming. Under the scenario that best matches current national commitments (RCP4.5), we estimate that in the transient stage, two tipping points will be crossed. If radiative forcing is then held fixed after the year 2100, a further six tipping point thresholds are crossed. Achieving a trajectory similar to RCP2.6 requires reaching net‐zero emissions rapidly, which would greatly reduce the likelihood of tipping events. Plain Language Summary The importance of reaching net‐zero greenhouse gas emissions to help avoid dangerous anthropogenic climate change is widely acknowledged. However, current national commitments do not align with this target and instead will lead to about 2.7°C warming by 2100. If the large‐scale carbon dioxide removal needed to reach net‐zero emissions is unfeasible and instead, the remaining hard‐to‐mitigate emissions approximately balance natural sinks, atmospheric greenhouse gas (GHG) concentrations will remain constant. Such fixed GHG levels will result in continued warming until the climate system reaches a state of radiative balance, which we call “committed warming.” We investigate the committed warming associated with the CO2 equivalent (CO2e) for each year for three emission scenarios. Critically, we then examine the probability of breaching tipping point thresholds at different levels of committed warming, finding that under the scenario that best matches current national commitments, we will be committed to crossing the critical temperature threshold for six key climate tipping points by 2100. Maintaining radiative forcing at only slightly elevated levels above present GHG concentrations will substantially alter parts of the Earth System through such “locked‐in” impacts. Society will only be able to avoid breaching tipping point thresholds through rapid and very substantial reduction of human emissions. Key Points We conduct a thought experiment on equilibrium global warming and tipping point likelihood under constant greenhouse gas concentration scenarios Maintaining radiative forcing at or above current levels would commit multiple parts of the climate system to passing tipping points Only a lower emissions scenario, which would require rapidly reaching net‐zero emissions, avoids crossing most climate tipping points

The original version of this Article contained an error in Table 1, in which some cell boundaries were drawn incorrectly. The correct version of Table 1 contains the correct boundaries and capitalizes a few terms, while it also corrects the text in one cell from “elevation change” to “Surface elevation”. This has been corrected in both the PDF and HTML versions of the Article.