In the final part of Dr. Emily Shuckburgh’s article, she turns to extreme weather and the challenges of responding to this in order to limit warming to 1.5C. Dr. Emily Shuckburgh is a climate scientist at the British Antarctic Survey, and is at the forefront of observing the dramatic and shocking changes in our ice sheets and greenhouse gas levels. Click to read part one and part two of the article.

We are already experiencing increased risk of extreme weather due to climate change

Extreme weather events such as heatwaves, droughts, floods and storms can cause major damage and disruption to human society, with large financial costs and sometimes loss of life. Statistics on natural catastrophes world-wide shows a substantial increase over the past 35 years in the annual total for the number of recorded weather-related events such as storms and floods.

Around the world, temperature and rainfall records are being broken again and again as what were once extreme conditions are starting to become normal. The population-weighted average temperature, which accounts for where people live, has been increasing at more than twice the rate of the global-average. Extreme heat, especially when combined with high humidity, can prove deadly for vulnerable people. One recent study estimated that already today 30% of the world’s population experience such potentially deadly conditions each year.

Evaluation of recent catastrophes has revealed numerous cases where the risk of occurrence of extreme weather has increased as a consequence of the climate change we have already seen. The connection with an increased risk of heatwaves is evident, but a warmer atmosphere also holds more water, giving rise in places to more intense rains and increased flood risk.

Analysis indicates that the kind of heavy downpours responsible for some of the terrible flooding of recent years in the UK have become more likely because of climate change. More than 50,000 households and approaching 10,000 businesses were innundated during some of the floods, critical infrastructure was destroyed, a number of people sadly lost their lives and billions of pounds of damage was caused.

Hurricanes provide a stark reminder of the power of nature to wreak devastation on even the most advanced of our societies. The mechanics of tropical cyclones and how they interact with our changing climate is extremely complex, however, it is clear that increases in heavy rainfall, combined with sea level rise and can exacerbate the flooding from hurricane-induced storm surges.

In 2016, a severe drought in Southern Africa resulted in millions of people in need of humanitarian assistance in countries such as Malawi. The other side of the world, Southeast Asia experienced record-breaking heat, with temperatures in Thailand soaring above 40°C. In both cases it has been determined that climate change exacerbated the effects of El Niño. The risks of these two far-away events were correlated. The systemic risks arising from such correlated events can easily be underestimated.

Warming due to our emissions from the pre-industrial period to the present will persist for centuries to millennia and these alone will continue to cause further long-term changes in the climate system, such as sea level rise.

Greenhouse gas emissions continue to increase

The first report of the Intergovernmental Panel on Climate Change warning the threat of climate change due to greenhouse gas emissions was completed in 1990. At the time, total carbon dioxide emisions were about 27 GtCO2/yr. Since then, annual emissions of carbon dioxide from fossil fuel use and industry have grown substantially (they have been growing at about 2%/yr over the past decade) and now stand at over 37 GtCO2. An additional 5 GtCO2 is emitted each year as a result of land use, land-use change, and forestry, meaning the total carbon dioxide emissions are now around 42 GtCO2/yr, more than 50% higher than they were in 1990. In terms of per capita emissions, China has recently exceeded the European average and stands at almost double the global average, although it still amounts to less than half the US per capita emissions.

Methane is the second most important long-lived greenhouse gas and at present it contributes about one sixth of the greenhouse effect. The levels of atmospheric methane have increased by more than 150% since pre-industrial times. This long-term increase is mostly attributed to human activity, including cattle breeding, rice agriculture, landfills, biomass burning and fossil fuel extraction.

Time is running out; we are currently on-track for 3°C by end of century

In 1992, the United Nations Framework Convention on Climate Change (UNFCCC) was adopted with the objective of curbing greenhouse gas emissions to prevent dangerous climate change. In 2015, at the 21st Conference of the Parties to that convention, the nations of the world committed within the Paris Agreement to hold the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C, recognizing that this would significantly reduce the risks and impacts of climate change.

At present, tempertures are increasing at about 0.2°C per decade due to past and ongoing emissions. With temperatures already 1°C of warmer than pre-industrial times, that means we are on-course to surpass the level of 1.5°C of warming sometime between 2030 and about 2050. Despite the declared aims of the Paris Agreement, pathways reflecting current nationally stated mitigation ambition until 2030 are broadly consistent with cost-effective pathways that result in a global warming of about 3°C by 2100, with warming continuing afterwards. Greater ambition is required to limit temperature rise to the Paris Agreement commitments.

The amount of carbon dioxide that can be released before dangerous levels of warming are reached can be seen as a “carbon budget” which equates to the total cumulative emissions of CO2 since the preindustrial period. The more emissions we generate now, the faster we will have to slash them later to stay within the budget; and we may find that the speed of cuts then required is unachievable, even with new technologies. By the end of 2017, cumulative emissions since the preindustrial period are estimated to have reached approximately 2200 GtCO2. The remaining budget to allow a good chance of staying below 1.5°C is estimated to be around 400-550 GtCO2; at the current rate of emissions of 42 GtCO2/yr that implies we are heading towards the budget for 1.5°C being exhausted within the next ten to fifteen years.

Risks increase with warming, posing threats for human wellbeing as well as the natural world and the services it provides

Limiting global warming to 1.5°C rather than 2°C would result in considerably less climatic change, for example, a reduced risk of extreme heat and of drought in places, and a smaller total land area/number of people at risk from inland and coastal flooding. It would also prevent the thawing of an area of permafrost in the range of 1.5 to 2.5 million km2, equivalent to one to two times the area of Canadian Arctic, and reduce the odds of an ice-free Arctic summer from 1-in-10 to 1-in-100 years.

Limiting warming to 1.5°C, compared with 2ºC, is also projected to result in smaller net reductions in yields of maize, rice, wheat, and potentially other cereal crops, and it would mean fewer heat-related illnesses and deaths, and less risk from vector-borne diseases, such as malaria and dengue fever.

In terms of the natural world, between 2-3 times more plants and animals are anticipated to experience severe habitat loss at 2°C compared with 1.5°C, and with that would come the loss of the services provided to human society. Moreover, it is thought while a small portion of coral reefs would remain at 1.5°C, virtually all would be lost at 2°C, succuming tot he combined influence of warming seas and ocean acidification caused by CO2 emissions. Indeed, comparable rates of acidification have not been seen since 250 million years ago, when the largest ever mass extinction of species took place. Again, this is not only an environmental threat – healthy coral reefs support commercial and subsistence fisheries, jobs and businesses through tourism and recreation, and contribute billions of dollars each year to the global economy.

Overall, climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth are projected to increase with 1.5°C of warming and to increase further with 2°C.

Warming increases the risk of a catastrophic shock

Recent millennia have been characterised by unusual climate stability. But it is clear that as temperatures increase, the risk of triggering catastrophic shocks – climatic black swan events – increases. For some systems this is a concern even within the Paris Agreement limits.

We know that dramatic and rapid regional change in temperature has occured in the past: in the North Atlantic, there are more than 20 examples of this in the last 100 thousand years. The potential for such large changes is a fundamental non- linear characteristic of the Earth system.

Modest temperature rise, for example, may threaten the vast ice sheets covering Greenland & West Antarctica. There is evidence that ice sheet disintegration could be triggered around 1.5°C to 2°C of global warming, eventually leading to many metres of sea level rise, transforming global coastlines.

The majority of large cities around the world are located in low-lying coastal regions, often for good historical reasons since they were important trading ports. Moreover, many of the developing megacities in Asia and elsewhere are located on or near the coast. Just a few tens of centimetres of sea level rise, especially in combination with heavy rain and storm surges, could destroy infrastructure and displace hundreds of millions of people; a black swan event involving the polar ice sheets would be devastating. Are these risks being fully accounted for in development planning or scenario analysis?

What response is required to limit climate disruption?

We need to reach net-zero by 2050 to meet 1.5°C goal

Let me now turn to the scale and urgency of the challenge of responding to climate change in a way that meets the Paris Agreement objectives. It is evident that the later emissions reductions begin, the more accelerated they will need to be for global temperatures to remain within the limits agreed in Paris.

The recent IPCC special report found that to keep temperatures below about 1.5°C requires global CO2 emissions to decline by about 45% from 2010 levels by 2030 and to reach net zero around 2050, as shown in Figure 2.

Source: IPCC Special Report on 1.5C, October 2018

This is a dramatic change of trajectory. In broad terms climate action means a transformation unprecedented in terms of scale, reversing over the next decade the emissions increases that have occured over the past four decades so that by 2030 we return to the 1980 CO2 emissions levels. Deep reductions in non-CO2 emissions, such as methane and nitrous oxide, are also required. Moreover, reversing ocean acifidication and limiting on-going sea level rise is likely to require a commitment to net negative CO2 emissions in the long-term.

This requires transformation across all sectors, which of course comes with its own risks for businesses and investors. Electricity generatation needs to be essentially decarbonised globally by 2050, with renewables growing enormously to supply 70-85% of electricity and any remaining fossil fuel use being coupled to carbon capture and storage systems. The IPCC report notes that some fossil investments made over the next few years – or those made in the last few – will likely need to be retired prior to fully recovering their capital investment or before the end of their operational lifetime. A reduction of at least 75-90% is also required in terms of industrial emissions by 2050, requiring the deployment of both existing and new technologies and practices, including electrification, hydrogen, sustainable bio-based feedstocks, product substitution, and carbon capture, utilization and storage. Other changes include, for example, major alterations to land use. Moreover, it is clear that substantial amounts of CO2 will need to be extracted from the atmosphere to compensate for residual emissions. The carbon dioxide removal approaches that are required to achieve this come with a complex set of risks, costs, trade-offs and benefits.

If managed appropriately, limiting warming to 1.5°C can postively support the delivery of the UN Sustainable Development Goals. Improved air quality resulting from required reductions in many non-CO2 emissions would provide direct and immediate health benefits: indoor air pollution currently causes millions of deaths each year and outdoor air pollution causes millions more. There are also clear co-benefits in terms of greater access to afordable and clean energy, especially when a billion people worldwide still live without access to electricity. Moreover, the number of people both exposed to climate-related risks and susceptible to poverty could be reduced by up to several hundred million by 2050 if temperatures are kept to 1.5°C instead of 2°C.

Businesses and investors must be part of the solution

The greenhouse gas emissions from the 100 largest emitting companies of the world (including their value chains) account for approximately a quarter of global annual emissions. The top 250, which include businesses in the oil, gas, utility, automotive, aircraft, manufacturing, steel, mining and cement sectors, account for approximately one third of the global total. It is evident, therefore that businesses play a critical role in responding the the scale and urgency of the climate challenge as laid out by the scientific evidence.

Those operating in heavily carbon intensive sectors must rapidly diversify and decarbonize their business models if the world is to achieve the level of emissions reductions outlined above. Others too must show leadership to embed the wide-ranging transformations that are required over the coming decades.

Each year’s delay in reduction of global emissions necessitates a steeper reduction curve in the future, likely increasing the cost and complexity of the required transformations, and decreasing the probability of meeting targets required for limiting disruptive climate events.

Moving beyond pure financial considerations, the science is absolutely clear that decisions taken today will affect the course of the rest of this century and beyond and determine the destiny of our children, grandchildren and their children.

This article was originally published as one piece and has been kindly reproduced on the POW UK blog in three parts with Dr. Emily Shuckburgh’s permission. To find out how you can help, check out the actions on our POW Mountain.


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