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ZEROing IN on this critical decade for climate: Insights from the latest IPCC reports on the Paris Agreement, 1.5°C, and climate impacts

The latest ZERO INreport from the CONSTRAIN project dives into the science set out in the recent Intergovernmental Panel on Climate Change assessments. It investigates what our climate future could look like, depending on whether we take action in line with the Paris Agreement, or decide to follow current national policies and plans.
a flooded city from above
An image from the report of a flooded city.


This November sees world leaders gather in Egypt for the COP27 climate summit, at the end of a year hit by multiple climate disasters causing billions of dollars of damage.

Meanwhile, greenhouse gas emissions have bounced back above pre-pandemic levels, highlighting the huge gap between the words set out in international climate commitments and the scale of action needed to actually achieve the Paris Agreement.

The fourth ZERO IN report looks at how cutting emissions in this critical decade for climate can limit temperature rise and other climate impacts in the near-term. In doing so it provides supporting information on the latest Intergovernmental Panel on Climate Change (IPCC) reports, unpacking the level of action needed to slow down and even halt warming in the coming decades, in line with the Paris Agreement.

It also shows how increased ambition and action can limit the worst climate impacts, from floods and cyclones to heatwaves, across the world. It investigates what our climate future could look like by 2050, depending on whether we take action in line with the Paris Agreement, or decide to follow current national policies and plans which still largely lack the action and ambition needed to stop global warming.

This report follows the 2021 ZERO IN report.

This weADAPT article is an abridged version of the original text, which can be downloaded from the right-hand column. Please access the original text for more detail, research purposes, full references, or to quote text.

Why is this the critical decade for climate?

The latest climate science confirms that limiting warming to 1.5°C is still technically feasible – albeit increasingly difficult, with deep, rapid, and immediate emissions reductions needed across all sectors. Achieving this is a matter of political will: current climate policies and targets will not get us there, andthe choices made between now and 2030 will be critical.

Our ability to keep temperature rise to below 1.5°C is therefore largely dependent on governments’ collective action in the very near term. By 2023 we will be well into ‘the critical decade’, and by delaying action we are not only increasing the scale and immediacy of the emissions cuts needed to prevent the worst impacts of climate change, but also the severity of the impacts we do experience.

The IPCC is incredibly clear on this – we need to target larger emissions cuts, and achieve them by 2030. We can still have a good chance of keeping global warming to 1.5°C this century, in line with the Paris Agreement. Yet without increased ambition and action this decade, our ability to keep temperature rise below 1.5°C will be lost.

Methodology and results

The latest IPCC report looks at how different climate change mitigation choices across major economic sectors translate into future emissions and temperatures.

Using a simple climate model, we translated these choices into what they would mean for warming rates between now and 2050, and for the total change in temperature we could see by 2050.

We found that immediate and rapid energy system transformations and emissions cuts would slow down the rate of global warming between now and 2050. In fact, the current warming rate of around 0.2°C per decade could well be halved in the 2030s, and warming could be halted or even begin to reverse by the middle of the century.

In contrast, if countries do not raise their ambitions and instead continue to follow their current policies, warming would essentially continue at its current very high rate.

 Warming per decade up to 2050 of selected emissions pathways

We also translated these warming outcomes into climate impacts, building on work by the Climate Action Tracker, a tool for tracking government climate action and measuring it against the Paris Agreement temperature goals.

We found that relatively small differences in warming rates over the coming decades, and in absolute warming by 2050, still have significant implications for climate impacts

 Examples of climate impacts in 2050 as a result of three different global warming levels (blue: 1.5°C; orange: 1.7°C; pink: 1.8°C) in different countries.

Outcomes and impacts

These findings highlight the need for deep, rapid, and immediate emissions reductions across all sectors, starting now and reaching net zero around mid-century, if we are to stand a good chance of keeping global warming within 1.5°C, in line with the Paris Agreement. It also shows how ambitious climate action could slow down and stop – or even reverse – global warming by 2050.

The results also shine a light on why 1.5°C is not just a number: every fraction of a degree matters. More temperature rise will lead to greater climate impacts and costs, from flooding in COP27 host country Egypt to cyclones, heatwaves and loss of productivity across the world.

This is especially true at the regional scale with some countries more strongly affected, or less able to respond, than others. For instance, if temperatures increased by 1.7°C rather than 1.5°C by 2050, the additional warming could increase the number of people exposed to heatwaves in some countries by around a third.

Limiting warming to 1.5°C will help to avoid the worst of it.


We are already well into this critical decade for climate, and every moment of delay makes it increasingly difficult to prevent the worst climate impacts from hitting the most vulnerable societies across the world.

Every tonne of greenhouse gas emissions counts. At COP27, world leaders can either watch as global warming continues to wreak havoc, or play their part in making this critical decade a true success for climate action.

Suggested Citation:

CONSTRAIN (2022) ZERO IN ON: The Critical Decade – Insights from the Latest IPCC Reports on the Paris Agreement, 1.5°C, and Climate Impacts. The CONSTRAIN Project Annual Report 2022, Accessed from

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