The new report from the International Panel on Climate Change is a wake-up call for urban leaders everywhere. It alerts them to the likely consequences of climate change and provides a stark warning that they must prepare to protect their citizens now.

It confirms that there is absolutely no doubt that the climate system is warming, for each of the last the decay that's has been successively warmer at the Earth's surface than any preceding decade since 1850.

The report, Climate Change 2014: Impacts, Adaptation, and Vulnerability, details the impacts of climate change to date, the future risks from a changing climate, and the opportunities for effective action to reduce risks. It has been compiled by 309 coordinating lead authors, lead authors, and review editors, drawn from 70 countries, plus 436 contributing authors, and a total of 1,729 expert and government reviewers.

The report identifies vulnerable people, industries and ecosystems around the world and urges everyone to prepare means of protecting them as well as reducing greenhouse gas emissions.

The conclusions are unequivocal. “We live in an era of man-made climate change,” said Vicente Barros, Co-Chair of Working Group II. “In many cases, we are not prepared for the climate-related risks that we already face. Investments in better preparation can pay dividends both for the present and for the future.”

A video of the press conference is here.

The report uses four possible scenarios: two extreme ones in which, on the one hand, we take all the necessary steps required to reduce emissions, and on the other, one in which emissions continue to increase through burning of fossil fuels. In between there are two middle-route scenarios.

The risk in the future from a changing climate depend strongly on the choices we make now, said Barros. "Increasing magnitudes of warming increase the likelihood of severe and pervasive impacts that may be surprising or irreversible," warns the press release accompanying the report.

“With high levels of warming that result from continued growth in greenhouse gas emissions, risks will be challenging to manage, and even serious, sustained investments in adaptation will face limits,” said Chris Field, co-chair of the working group II that produced the report.

“Part of the reason adaptation is so important is that the world faces a host of risks from climate change already baked into the climate system, due to past emissions and existing infrastructure,” said Barros.

Field offered a glimmer of hope: “We definitely face challenges, but understanding those challenges and tackling them creatively can make climate-change adaptation an important way to help build a more vibrant world in the near-term and beyond,” he said.

He urged the sharing of best practice, and the use of analytical systems to help us understand what works and what doesn't in adaptation.

There is one further working group report to come in this cycle, in October: a synthesis report. Working Group 1's report was released last September.

The report consists of two volumes:

  1. a Summary for Policymakers, Technical Summary, and 20 chapters assessing risks by sector and opportunities for response. The sectors include freshwater resources, terrestrial and ocean ecosystems, coasts, food, urban and rural areas, energy and industry, human health and security, and livelihoods and poverty.
  2. 10 chapters  that assess risks and opportunities for response by region: Africa, Europe, Asia, Australasia, North America, Central and South America, Polar Regions, Small Islands, and the Ocean.

The scientific findings

Projected sea level changeMost - over 90% - of the stored solar energy that has been retained by the blanket of greenhouse gases around the planet is to be found in the oceans, which have also absorbed about 30% of the greenhouse gases emitted by the burning of fossil fuels by humans. The Greenland and Antarctic ice sheets have been shrinking over the last 20 years, and Arctic sea ice and Northern Hemisphere spring snow cover have continued to retreat.

The sealevel is continuing to rise: between 1901 and 2010 it rose by an average of 0.19m. The oceans are also acidifying: the pH of the ocean surface water has decreased by 0.1 since the beginning of the industrial era. This has a profound effect on lifeforms dwelling there and this effect is very likely to continue.

The IPCC report confirms that carbon dioxide is the gas producing the most global warming effect. The effect is increasing rapidly: the report gives the total man-made pressure on temperature increases to be 43% higher in 2011 than in 2005. "Human influence on the climate is clear," it says. Sealevel will continue to rise and threaten low-lying and coastal areas

Improvements in climate models since 2005 only serve to confirm this. "Observational and model studies of temperature change, climate feedbacks and changes in the Earth's energy budget together provide confidence in the magnitude of global warming in response to past and future forcing," the scientists affirm.

projected precipitation rises in the tropics

A regional projection map from the AR5 report: the annual mean change in precipitation, and relative sea surface temperature change (colour contours at intervals of 0.2°C; negative dashed) to the tropical (20°S to 20°N) mean warming in a high-continuing-emission scenario. 

In their firm language, the scientists warn that "limiting climate change will require substantial and sustained reductions of greenhouse gas emissions". On present trends global surface temperature change by the end of this century is likely to exceed 1.5°C relative to 1900, even if we take very strong action now. If we do not take action, much higher temperature increases are likely and they will continue for centuries to come. "This represents a substantial multi-century climate change commitment created by past, present and future emissions of CO2," says the report.

The report makes plain the consequences of this: greater increases in storms and rainfall in certain areas and prolonged drought in others. There are unknown consequences: for example ocean circulation patterns may change which will have a knock-on effect on agriculture and fisheries. The sources of our food supplies are under peril.

Samantha Smith, leader of the WWF Global Climate & Energy Initiative says the report highlights, for the first time, the dramatic difference of impacts between a world where we act now to cut emissions, which now come mostly from using fossil fuels; and a world where we fail to act quickly and at scale.

“This report tells us that we have two clear choices: cut emissions now and invest in adaption - and have a world that has challenging and just barely manageable risks; or do nothing and face a world of devastating and unmanageable risks and impacts.”