What does 1.5C mean in a warming world?

Matt McGrath BBC 2 Oct 18;

Over the past three years, climate scientists have shifted the definition of what they believe is the "safe" limit of climate change.

For decades, researchers argued the global temperature rise must be kept below 2C by the end of this century to avoid the worst impacts.

But scientists now argue that keeping below 1.5C is a far safer limit for the world.

Everyone agrees that remaining below that target will not be easy.

This week in South Korea, researchers will report on the feasibility and costs of achieving this lower limit.

The scientists of the Intergovernmental Panel on Climate Change (IPCC) are gathering in the city of Incheon to hammer out a plan in co-operation with government delegates, on the actions that would need to be taken to meet this new goal.

So why has the goal changed?

In a word - politics.

The idea of two degrees as the safe threshold for warming evolved over a number of years from the first recorded mention by economist William Nordhaus in 1975.

By the mid 1990s, European ministers were signing up to the two-degree limit, and by 2010 it was official UN policy. Governments agreed in Cancun to "hold the increase in global average temperatures below two degrees".

However, small island states and low-lying countries were very unhappy with this perspective, because they believed it meant their territories would be inundated with sea water as higher temperatures caused more ice to melt and the seas to expand.

They commissioned research which showed that preventing temperatures from rising beyond 1.5C would give them a fighting chance.

At the ill-fated Copenhagen climate summit in 2009, the climate-vulnerable nations pushed for the lower figure, but their efforts were lost in the blame-game that followed the collapse of the conference.

But the idea didn't go away completely - and by the time of the Paris negotiations in 2015, it emerged centre-stage as French diplomats sought to build a broad coalition of rich and poor nations who would support a deal.

It worked.

What difference does half a degree actually make?

More than you might think!

Leaked drafts of the IPCC Summary for Policymakers that will be published after a week of haggling with government delegates in South Korea point to some major differences in terms of the impacts on the world of 1.5 and 2C. We've summarised the main ones here:

"Two degrees is no longer the two degrees we thought it was," said Kaisa Kosonen from Greenpeace who is monitoring the progress of the IPCC 1.5C report.

"It's increasingly becoming meaningless as a climate goal, when you look at the risks that would come with it and what we are already witnessing with one degree - why would you have a goal that doesn't protect anything that we care about?"

How hard will it be to keep below the limit?
Very - the world has already warmed by around one degree and according to leaked drafts of the 1.5 report, we will sail past that limit by around 2040.

The new IPCC report won't tell governments what to do but will instead set out a range of approaches that will likely involve heavy cuts in carbon emissions, a rapid transition to renewable energy and lifestyle and dietary changes as well.

What happens if we go beyond 1.5?

The IPCC have spent a lot of time considering that question and have devised a cunning plan!

In their draft reports they talk about "overshoot", meaning that in many scenarios they expect temperatures to go beyond 1.5 but they believe they can be clawed back below the limit by using a range of technologies that will remove carbon dioxide from the air - these range from planting trees to more complex, untested machines.

Some experts, though, believe that there are considerable risks to this approach.

"A species that goes extinct at two degrees will still be extinct if you come back down to 1.5C," said Dr Steven Cornelius from WWF, a former UK government IPCC negotiator.

"Some things may come back but some things are irreversible, in terms of taking a risk you'd want to try and keep below 1.5, and clearly that means faster, deeper earlier emissions cuts, and it probably means carbon dioxide removal. But these technologies - some of them we know what to do, but some are early days and need to be assessed."

Are there any hopeful signs?

Surprisingly, yes!

While the task of limiting the global temperature rise to 1.5C this century is massive, there are some indicators on the horizon that show that some governments are recognising the seriousness of the issue and are taking steps to deal with it.

Just a few days ago, the UK government committed to achieving net zero emissions by 2050 when it joined 18 other nations in the Carbon Neutrality Coalition.

Some environmentalists believe that the pathway to keeping temperatures down to 1.5 can be done without resorting to mechanical devices or planting billions of trees.

"If we have very rapid emissions reductions and couple that with massive scaling up of restoration of land and changes in our food system to reduce meat consumption, we can get to 1.5C in a way that creates lots of wellbeing for people," said Hannah Mowat from Fern.

"It creates better air and reduces levels of obesity. It's a world we want to say yes to, rather than a further industrialisation of our landscapes."

UN report spotlights government inaction on climate
Marlowe HOOD AFP Yahoo News 1 Oct 18;

Diplomats gathering in South Korea Monday will find themselves in the awkward position of vetting and validating a major UN scientific report that underscores the failure of their governments to take stronger action on climate.

The UN special report on global warming of 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial levels began as a request from the 195 nations that inked the Paris Agreement in 2015.

That landmark pact called for capping the rise in global temperature to "well-below" 2C, and invited countries to submit voluntary national plans for reducing greenhouse gas emissions.

To the surprise of many -- especially scientists, who had based nearly a decade of research on the assumption that 2C was the politically acceptable guardrail for a climate-safe world -- the treaty also called for a good-faith effort to cap warming at the lower threshold.

At the same time, countries asked the UN's climate science authority, the Intergovernmental Panel on Climate Change (IPCC), to detail what a 1.5C world would look like, and how hard it might be to prevent a further rise in temperature.

Three years and many drafts later, the answer has come in the form of a 400-page report -- grounded in an assessment of 6,000 peer-reviewed studies -- that delivers a stark, double-barrelled message: 1.5C is enough to unleash climate mayhem, and the pathways to avoiding an even hotter world require a swift and complete transformation not just of the global economy, but of society too.

With only one degree Celsius of warming so far, the world has seen a climate-enhanced crescendo of deadly heatwaves, wild fires and floods, along with superstorms swollen by rising seas.

- Line-by-line vetting -

"I don't know how you can possibly read this and find it anything other than wildly alarming," said Peter Frumhoff, director of science and policy at the Union of Concerned Scientists, a Washington-based research and advocacy group, referring to the draft Summary for Policy Makers.

Government representatives -- often the same ones in the trenches at UN climate negotiations -- will spend the entire week going through the 22-page executive summary, line-by-line.

With scientists at their elbow, they will check it against the underlying report and, if the past is any guide, attempt to blunt conclusions deemed inconvenient by their governments.

"Some countries, such as Saudi Arabia, have threatened to be obstructionist," said one of the report's authors.

China is said to have reservations on the chapters outlining policy options, concerned that some of the measures outlined may be too ambitious.

But the joker in the pack is the United States, several delates and observers noted.

"This is the first report coming up for approval since the Trump administration took office," said Michael Oppenheimer, a professor of geosciences and international affairs at Princeton University, and an IPCC author on a another report-in-progress.

"That's a real wild card."

- US a 'wild card' -

There are few clues as to what the United States might say or do in Incheon, which has left a lot of people nervous.

"The US could, as they have in the past, support the science," said one contributing author.

"Or they could become obstructionist -- maybe Fox News will decide to shine a spotlight on the meeting."

A State Department spokesperson confirmed to AFP that veteran climate diplomat Trigg Talley will head the US delegation, a development one veteran IPCC author described as "reassuring."

"Never in the history of the IPCC has there been a report that is so politically charged," said Henri Waisman, a senior researcher at the Institute for Sustainable Development and International Relations, and one of the report's 86 authors.

Governments looking for a straightforward answer to the question of whether the 1.5C target can be reached are likely to be disappointed, he added.

"The report isn't going to simply say 'yes' or 'no'," he told AFP.

"Our goal was to put as much information as possible into the hands of policy makers so they can step up to their responsibilities."

Many scientists say the goal is feasible on paper, but would require political will and economic transformations that are not on the near-term horizon.

"In my view, 1.5C stabilisation is extremely difficult if not impossible at this point, while 2C stabilisation is an uphill challenge but doable," Michael Mann, director of the Earth System Science Center at Pennsylvania State University, told AFP.


Climate changing faster than feared, but why are we surprised?
Marlowe HOOD AFP Yahoo News 5 Oct 18;

Incheon (South Korea) (AFP) - Nearly every day, peer-reviewed studies on global warming warn that deadly impacts will come sooner and hit harder than once thought.

Virtually none, however, suggest that previous predictions of future heatwaves, droughts, storms, floods or rising seas were overblown.

And so, as the world's nations huddle in South Korea to validate the first major UN assessment of climate science in five years, one might ask: have we underestimated the threat of global warming?

The Intergovernmental Panel on Climate Change (IPCC) report on capping the rise in Earth's surface temperature at 1.5 degrees Celsius (2.7 degrees Fahrenheit) above preindustrial levels has not been finalised, with delegates predicting the five-day meet -- due to end Friday -- will go deep into overtime.

But a new draft of the 28-page summary for policymakers, obtained by AFP, makes it alarmingly clear that the two-degree ceiling long seen as the guardrail for a climate-safe world is no longer viable.

With only one degree Celsius of warming so far, the planet is reeling from a crescendo of lethal and costly extreme weather events made worse by climate change.

"Things that scientists have been saying would happen further in the future are happening now," Jennifer Morgan, Executive Director of Greenpeace International, told AFP.

"We thought we had more time, but we don't."

The landmark 2015 Paris Agreement enjoins its nearly 200 signatories to hold warming to "well below" 2C -- and 1.5 degrees if possible, an aspirational goal that gave rise to the IPCC report.

- 'Short-termism' -

Many scientists point out that warnings of a climate-addled future date back decades.

The 1972 UN Conference on the Human Environment, for example, foresaw the possibility of "global and catastrophic effects" from a 2C jump in temperatures caused by carbon dioxide emissions.

"Many scientists have long known that human-induced climate change could have dire consequences," said Jean-Pascal van Ypersele, a professor of climatology at Universite Catholique de Louvain, and a former IPCC vice-chair.

"Those who have underestimated the severity of climate change are mostly policymakers."

Van Ypersele chalked up political inaction to "short-termism" -- election cycles trumping long-term issues -- and deliberate campaigns led by the fossil fuel industry to sow doubt about the validity of climate science.

But Wolfgang Cramer, research director at the Mediterranean Institute for Biodiversity and Ecology and a lead author of the IPCC report, disagreed.

"Scientists should be a bit more self-critical," he told AFP in Incheon. "Over the last 15-20 years, we have focused mostly on the impacts of a 2.5C, 3C and even 4C world."

"So when leaders asked, 'if we shoot for 1.5C, what will it take?', we could only answer: 'We don't really know'."

- Models inadequate -

Indeed, the vast majority of 200-odd climate models used to generate IPCC projections in its last major report, published in 2013, presumed a 2C benchmark. Only a handful even considered a 1.5C world.

And for good reason: Though loosely tethered to science, the 2C target emerged mostly from the political turmoil of the 2009 Copenhagen summit, and set the research agenda for nearly a decade.

Those earlier models were inadequate, said Michael Mann, director of the Earth System Science Center at Pennsylvania State University.

"Overly conservative, they failed to capture the full impacts of a warming planet on extreme weather events such as those that broke out across North America, Europe and Asia this summer," he told AFP.

The models also underestimated Arctic sea ice loss, along with the pace at which the ice sheets atop Greenland and West Antarctica -- with enough frozen water to add 13 meters to sea levels -- are disintegrating.

These "feedback effects", both a cause and an effect of global warming, are especially difficult for models to capture, Mann noted.

Finally, science is inherently conservative, doubly so when it comes to the IPCC, whose credibility -- constantly under fire -- depends on never exaggerating the threat.

"There is a cultural tradition in science, especially climate science, to not want to be alarmist," said Peter Frumhoff, director of science and policy at the Union of Concerned Scientists, a Washington-based research and advocacy group.

The 2013 IPCC report, for example, chose to not include in its sea-level projection the contribution of melting ice sheets, which have since emerged as the main driver.

"It was erring on the side of least drama," Frumhoff told AFP.