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News — An internationally respected group of scientists, including Professor Francois Engelbrecht from the University of the Witwatersrand, Johannesburg, have urgently called on world leaders to accelerate efforts to tackle climate change. Almost every aspect of the planet's environment and ecology is undergoing changes in response to climate change, some of which will be profound, if not catastrophic, in the future.

According to their study published in Science today, reducing the magnitude of climate change is also a good investment. Over the next few decades, acting to reduce climate change is expected to cost much less than the damage otherwise inflicted by climate change on people, infrastructure and ecosystems. Their research is being published only a few days ahead of the UN Climate Change Week in New York, in which international governments, business, academic institutions and non-profit organisations, among others, will be discussing the impacts of climate change on a global basis.

"Acting on climate change has a good return on investment when one considers the damages avoided by acting," says lead author, Professor Ove Hoegh-Guldberg from the ARC Centre for Excellence in Coral Reef Studies at the University of Queensland in Australia. The investment is even more compelling given the wealth of evidence that the impacts of climate change are happening faster and more extensively than projected, even just a few years ago. This makes the case for rapidly reducing greenhouse gas emissions even more compelling and urgent.

"We have underestimated the sensitivity of natural and human systems to climate change, and the speed at which these changes are happening," says Hoegh-Guldberg.

"We have underappreciated the synergistic nature of climate threats - with the outcomes tending to be worse than the sum of the parts. This is resulting in rapid and comprehensive climate impacts, with growing damage to people, ecosystems, and livelihoods."

For example, sea-level rise can lead to higher water levels during storm events. This can create more damage. For deprived areas, this may exacerbate poverty, creating further disadvantage. Each risk may be small on its own, but a small change in a number of risks can lead to large impacts.

Developing countries are especially vulnerable to climate change impacts, says co-author and Professor in Climatology at the Global Change Institute of the University of the Witwatersrand in South Africa, Francois Engelbrecht.

"The developing African countries are amongst those to be affected most in terms of impacts on economic growth in the absence of strong climate change mitigation," says Engelbrecht.

The southern African region may be regarded as a climate change hot-spot.

"The region has been warming drastically over the last five decades, at about twice the global rate of warming. Southern Africa is likely to become generally drier under low mitigation climate change futures."

Engelbrecht emphasises that by restricting global warming to 1.5°C future risks posed by droughts and heat-waves to the region can be reduced. At higher levels of global warming these risks are substantially higher, and more frequently occurring multi-year droughts may bring tipping points to the region in terms of water security, agriculture and livestock production.

Engelbrecht is a lead author of the IPCC Special Report on Global Warming of 1.5°C that was published in 2018. The new paper in Science reviews the findings of this report and assesses the latest scientific evidence of climate change impacts in a warming world, and the extent to which these impacts can be avoided/reduced through climate change mitigation.

In this research, Engelbrecht led the analysis of the identification of climate change hot spots and regional tipping points that may be reached under low mitigation climate change futures. Engelbrecht's research contributions to the Science paper also extended to the analysis of the projected changes in extreme weather events under different global degrees of global warming, with a focus on landfalling tropical cyclones and the drought in southern Africa.

Professor Daniela Jacob, co-author and Director of Climate Services Centre (GERICS) in Germany is concerned about these rapid changes associated with climate change - especially about unprecedented weather extremes.

"We are already in new territory," says Jacob, "The 'novelty' of the weather is making our ability to forecast and respond to weather-related phenomena very difficult."

These changes are having major consequences. The paper updates a database of climate-related changes and finds that there are significant benefits from avoiding 2oC of global warming and aiming to restrict the increase in global temperature to 1.5oC above pre-industrial global temperatures.

Professor Rachel Warren from the Tyndall Centre at the University of East Anglia in the UK assessed projections of risk for forests, biodiversity, food, crops and other critical systems, and found very significant benefits for limiting global warming to 1.5oC rather than 2oC.

"The scientific community has quantified these risks in order to inform policy makers about the benefits of avoiding them," says Warren.

Since the Paris Agreement came into force, there has been a race to quantify the benefits of limiting warming to 1.5oC so that policy makers have the best possible information for developing the policy required for doing it.

"If such policy is not implemented, we will continue on the current upward trajectory of burning fossil fuels and continuing deforestation, which will expand the already large-scale degradation of ecosystems. To be honest, the overall picture is very grim unless we act," says Warren.

A recent report from the United Nations projected that as many as a million species may be at risk of extinction over the coming decades and centuries. Climate change is not the only factor but is one of the most important ones.

Professor Michael Taylor, co-author and Dean of Science at the University of the West Indies says the urgency of dealining with climate change is not an academic issue. "It is a matter of life and death for people everywhere," he says. "People from small island States and low-lying countries are in the immediate cross-hairs of climate change. I am very concerned about the future of these people."

Professor Hoegh-Guldberg reiterated the importance of the coming year (2020) in terms of climate action and the opportunity to strengthen emission reduction pledges in line with the Paris Agreement of 2015.

"Current emission reduction commitments are inadequate and risk throwing many nations into chaos and harm, with a particular vulnerability of poor peoples. To avoid this, we must accelerate action and tighten emission reduction targets so that they fall in line with the Paris Agreement. As we show, this is much less costly than suffering the impacts of 2oC or more of climate change."

"Tackling climate change is a tall order. However, there is no alternative from the perspective of human well-being - and too much at stake not to act urgently on this issue."

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