Interview: Climate Scientist Tim Lenton indicates heat emergency in these two Indian cities

Climate change is a pressing global issue that demands our attention and action. As temperatures continue to rise and extreme weather events become more frequent, it is crucial to understand the implications of these changes for our planet and for human populations.

In an interview with Ground Report, Professor Tim Lenton, an esteemed expert in Climate Change and Earth System Science at the University of Exeter, sheds light on key aspects of climate change and its potential consequences.

With a focus on the projected rise in dangerously high temperatures by 2100, despite commitments made under the Paris Agreement, Professor Lenton provides valuable insight into the underlying factors and challenges hindering our progress.

He also delves into the concept of "climate niche" and its importance in understanding the impacts of climate change on human populations.

He explains how specific temperature thresholds, such as the definition of "dangerous heat," are determined and correlated with extreme heat events.

Discussing the goal of limiting global warming to 1.5°C instead of the projected 2.7°C, Professor Lenton emphasizes the importance of decisive climate policies and the need for a global transition to renewable energy sources.

Excerpts from the interview

Q: What causes the projected rise in dangerously hot temperatures by 2100, despite the Paris Agreement commitments?

A: The fact that countries' commitments to the Paris Agreement are not ambitious enough to meet the Paris Agreement and are currently mostly voluntary commitments with no guarantee or legal framework to ensure that they will be met.

Q: Could you explain the concept of "climate niche" and its importance in understanding the impacts of climate change on human populations?

A: The "climate niche" describes how human population density has historically depended on temperature and rainfall; this turns out to be highly conserved over time. There are a couple of population density peaks in the temperature niche, the largest around 12°C (mean annual temperature) and the second around 25°C which largely corresponds to the population of the Indian subcontinent. Between the two peaks, the intermediate temperatures tend to be drier and support fewer people. Above 25 °C, the population density drops sharply, as it does below 12 °C.

By trying to understand the impacts of climate change, we can project how future population density is expected to vary with climate and compare it to the historical distribution of population density with respect to climate. The mismatch indicates that people are living in future climates and at population densities that could only support fewer people in the past.

Q: How did you determine the specific temperature threshold of 29°C as definition of "dangerous heat" in your study?

A: This was defined as the mean annual temperature that almost no one experienced in the historical climate. We go on to show that, in recent observations, exceeding this mean annual temperature is correlated with exposure to extremes of dry heat (>40°C) and/or humid heat (wet bulb temperature >28°C).

Q: What are the Challenges to limit global warming to 1.5°C instead of 2.7°C and the role of climate policies in mitigation?

A: To accelerate the transition to renewable energy worldwide and associated transitions to more electrified transportation and heating. Policies to incentivize renewable energy and green technologies (eg electric vehicles) have already been shown in individual countries to be highly effective in triggering self-propelled change in the right direction. For example, in India, a public takeover of electric buses created a market and many reinforcing comments made the initiative spread rapidly.

Q: How likely are these scenarios and what would be the catastrophic consequences?

A: Warming of 3.6°C is the upper limit of what can be expected with current policies; I think it's defined as the 95% confidence interval, which would mean there's a 5% chance of that happening (or worse) with current policies.

Warming of 4.4°C corresponds to a world in which we are once again burning more fossil fuels. It is hard to say how likely it is that we will not comply with current climate policies and make it worse. Mostly, we want to believe that we will do better. Both are catastrophic scenarios that would pose an existential risk to current societies.

Are there specific regions within India that would be particularly vulnerable to dangerous heat?

A: Kolkata is one of the cities that would be exposed to dangerous heat in a 2.7°C warmer world. This assessment is influenced by recent heatwave-related deaths that have occurred in Kolkata, highlighting the city's vulnerability to extreme temperatures. In particular, even with 1.5°C warming, Chennai appears to be exposed, suggesting a high level of vulnerability to heat impacts in this region.

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