Hundreds of scientists from more than 70 countries helped pull together the new report from the Intergovernmental Panel on Climate Change (IPCC). Now it’s published, here’s what a few of them have to say about the report’s messages, and what should happen now.

“No question” the risks are real …

The IPCC report defines what the research community knows and doesn’t know about climate change. Chris Field, co-chair of the group that produced the report, told journalists on Sunday:

“Our job is to represent the full range of scientific and technical views on this critically important issues. When the IPCC does a report, what you get is the community’s position.”

And the report is unequivocal on the fact that human interference with the climate system is already occurring. Field adds:

“We see impacts from the equator to the poles and from the coast to the mountains. There’s no question we already live in a world that altered by climate change”

We’re already seeing more frequent extreme weather, food and water shortages, shrinking glaciers and species migrations, the report says. And as climate economist, professor Nicholas Stern,  points out:

“These are all happening after less than one degree centigrade of global warming.”

â?¦ and rising

The risks increase at higher levels of warming – but we’ll see different vulnerabilities in different places. Marginalised communities and those living in poverty worldwide will be hardest hit.

In the natural world, the effects “will be most felt in those ecosystems or regions which are already very vulnerable to change, such as coral reefs or small islands”, explains Dr Sally Brown from the Tyndall Centre for climate change.

Climate change isn’t acting in isolation. Dr Stephen Thackeray from the Centre for Ecology and Hydrology, says:

“[E]cosystems respond to the interactive effects of a changing climate and other stressors, such as habitat modification and pollution.”

Climate damages will be costly

How much will this all cost? This is a question that’s received a fair bit of attention. Field says the report’s estimate that two degrees of warming will cost the world “0.2 to 2 per cent of income” is “really old fashioned”. He says:

“[Those estimates] don’t include a lot of what we understand about the way climate change impacts work â?¦ They don’t capture a wide range of processes that are likely to be important.”

In other words, the costs are likely to be much higher – a the number is sandwiched with caveats to that effect. And the costs will be distributed unevenly across the world, with developing countries hardest hit. Dr Bhaskar Vira, member of the Royal Society Working Group on Human Resilience to Climate Change and Disasters says:

“Our moral compass needs to focus on the injustice that results from the unequal exposure of people around the world to the risks of climate change, caused by the actions and lifestyles of those at the opposite end of the income distribution.”

A “no regrets” strategy

Adaptation can go some way to buffering the blow of impacts that we can no longer avoid. professor Vincente Barros, co-chair of the new report, says:

“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”

It’s about making society more able to cope with present and future risk. Professor Paul Bates, from the Royal Society Working Group on Human Resilience to Climate Change and Disasters, says:

“We have good evidence that spending on disaster prevention is much more cost effective than spending on disaster clean up. This is a classic ‘no regrets’ strategy that can improve livelihoods and well-being now and in the future.”

For the UK, climate change means greater risk of heavy rain and flooding on the scale we saw this winter. Source: IPCC 5th assessment report: Impacts, vulnerability and adaptation.

But adaptation isn’t an alternative to bringing emissions down. The report makes clear that we can’t adapt indefinitely – at some point the costs become too high to bear. Field says:

“With high levels of warming â?¦ risks will be challenging to manage, and even serious, sustained investments in adaptation will face limits.”

Decision-making amid uncertainty

Mitigation is needed alongside adaptation to reduce the scale of future damage. As Daniella Schmidt, professor at the University of Bristol and lead author of the oceans chapter, explains:

“[T]he rate of climate change the greater the impact. This is a powerful signal that we can influence the impact of climate change in the future if we reduce the rate of carbon emissions and hence warming.”

What we do about climate change boils down to managing risk. Uncertainty on some specific details doesn’t justify delaying emissions cuts or reducing adaptation spending. Field says:

“Once we think of the challenge as one of managing risk – rather than of, oh once we know for sure what’s going to happen then we can do something – it becomes much more tractable. It becomes much more a question of figuring out what are the smart and effective things to do.”

A wake up call

Camilla Toulmin, director of the International Institute for Environment and Development, stresses the importance of international cooperation:

“[C]ountries, communities and companies must act fast to adapt to the changing climate â?¦ this drives home the urgency of global action to reduce greenhouse gas emissions.”

And Dr Hannah Cloke from the University of Reading says we should make sure we look past the next few years. She says:

“With increasingly difficult decisions ahead about which areas to protect, it’s important that we make sound, long term decisions based on solid evidence, not electoral cycles.”

And if a changing climate is too abstract for policymakers to grab on to, the threat to British honeybees might serve as a more tangible reminder, says Simon Potts, biodiversity expert at the University of Reading.

Changing temperature patterns mean bees are emerging earlier in the year, before there are enough flowering plants for them to feed on. Potts says:

“If policymakers want one reminder of a potential victim of climate change, they need look no further than their own gardens – and the contents of their kitchen cupboards.