Decades of insufficient action for mitigating GHG emissions have set the world on the current trajectory to overshoot the internationally agreed target of limiting global warming to 1.5°C, enshrined in the Paris Agreement. National mitigation commitments are inadequate to even stay well below 2°C of global warming, creating unacceptable risks for human societies and ecosystems, with vast yet unequally distributed costs. This is a dangerous gamble that could lead to irreversible impacts for life on Earth, including devastating loss of biodiversity and a rising risk of triggering climate tipping points. For example, megafires such as in Canada, May–July 2023; extreme rainfall and flooding as in Bulgaria, Greece, Libya, Spain and Turkey in September 2023; and extreme heatwaves across Europe, Asia and the Americas.

This year, we explain the looming inevitability of overshooting 1.5°C global warming (Insight 1), a situation that will entail a significant increase in risks and uncertainty. We call attention to the fast-shrinking carbon budget and emphasise the need for a managed and equitable fossil fuel phase-out (Insight 2). Considering the significance of carbon dioxide removal (CDR) in addressing these two issues, we outline the challenges related to deployment at scale, accounting and governance (Insight 3). This is particularly pressing in the context of research revealing key uncertainties regarding the extent to which global warming negatively affects the capacity of natural carbon sinks (Insight 4). This could complicate efforts towards temperature stabilisation and reversal, further adding to the urgency for decarbonising the global economy and being clear-sighted about the realistic role of CDR methods.

The research highlighted in this review points to the impending overshoot of 1.5°C in the short term (barring truly radical transformations). The risks we outline are an emphatic call to minimise overshoot, in both magnitude (by how much) and duration (for how long), while still acting to avoid it. New projects to expand fossil fuel infrastructure, such as the so-called carbon bombs, while clearly incompatible with the Paris Agreement, are still being approved by parties to the United Nations Framework Convention on Climate Change (UNFCCC) and the Paris Agreement. The expectations for COP28 will revolve around fossil fuel phase-out, a goal incorporated in the mandates of several governments and championed by the UN Secretary-General as part of the Acceleration Agenda at the Climate Ambition Summit 2023. To be successful, these negotiations must deliver on climate financing in support of just transitions in low- and middle-income countries.

In this report we stress the interwoven nature of biodiversity loss and climate change, requiring effective institutional cooperation for realising synergistic solutions (Insight 5). With climate impacts and vulnerabilities on the rise, this year’s report features advances on the scientific understanding of “compound events” (Insight 6) and the acceleration of mountain glacier loss (Insight 7); both of which we highlight as priority issues for adaptation planning, especially due to their impacts on food and water security. The urgency for mitigation is reinforced by the urgency for adaptation, especially for the most vulnerable regions and segments of society. Yet this urgency does not justify impositions on local communities.

We devote one Insight to immobility in the face of climate risks (Insight 8), aiming to shed light on an often overlooked dimension of the complex relationship between human mobility and climate change. We dedicate the last two Insights to the need for climate action to be deeply intersectional, reflective of the myriad interlinked sources and impacts of climate change, as well as potential co-benefits: incorporating, operationalising and centring justice in climate adaptation planning, emphasising the key role of locally led adaptation (LLA) efforts (Insight 9), and transforming food systems to reduce GHG emissions, while also increasing food security and biodiversity conservation, which can only happen with justice placed front and centre (Insight 10).

The Global Stocktake, while recognising the concerning trends resulting from insufficient mitigation so far, should reinforce the international commitment to mitigation to avoid long-lasting overshoot and keep peak warming as close to 1.5°C as possible.

We hope that this year’s 10 New Insights in Climate Science will be reflected in the outcomes at COP28:

  1. Taking unambiguous steps towards clear commitments for a managed phase-out of all fossil fuels, recognising the risks of prolonged overshoot, the uncertainties over the future of natural carbon sinks, and the remaining challenges for realising the complementary role of CDR.
  2. Strengthening the international support for adaptation and preparedness plans, in the face of emerging risks resulting from current and committed levels of global warming.
  3. Stressing the importance of food systems transformation as a key engine of climate action and climate justice.
  4. Advancing the integration of climate change and biodiversity in international policy agendas, and further promoting a holistic and equitable systems transformation premised on the interconnectedness of the challenges facing life on Earth.

All statements in this report are based on the following article and the references provided therein: Bustamante et al. (2023). Ten New Insights in Climate Science 2023/2024. Global Sustainability.

Explore 2023's 10 Insights in Climate Science


Overshooting 1.5°C is fast becoming inevitable. Minimising the magnitude and duration of overshoot is essential

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A rapid and managed fossil fuel phase-out is required to stay within the Paris Agreement target range

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Robust policies are critical to attain the scale needed for effective carbon dioxide removal (CDR)

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Over-reliance on natural carbon sinks is a risky strategy: their future contribution is uncertain

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Joint governance is necessary to address the interlinked climate and biodiversity emergencies

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Compound events amplify climate risks and increase their uncertainty

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Mountain glacier loss is accelerating

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Human immobility in areas exposed to climate risks is increasing

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New tools to operationalise justice enable more effective climate adaptation

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Reforming food systems contributes to just climate action

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