Rapid, far-reaching and unprecedented changes to all aspects of society are needed if global warming is to be limited to 1.5C, according to a new assessment by the Intergovernmental Panel on Climate Change.
The report was commissioned on foot of the Paris Climate Change Agreement three years ago, which was signed by 195 nations.
The assessment says the rate of warming caused by human activities is speeding up and that global emissions would need to fall by 45% by 2030, which is twice as fast as previously envisaged.
The report is a major wake-up to governments everywhere about needed urgency to do much more to tackle climate change.
It says that limiting global warming to 1.5C is possible within the laws of chemistry and physics.
However, it would require unprecedented and rapid changes to all aspects of society, including land, energy, industry, buildings, transport and cities.
The pace at which carbon emissions are targeted to fall over the next 12 years would need to double.
All net carbon emissions would have to be eliminated by 2050 rather than by 2080 as currently targeted. The benefits however would be significant.
Ten million people on small islands, low lying coastal areas, and river deltas would be protected by shaving 10cm off the rise in sea levels.
Several hundred million fewer people will be exposed to climate-related risks and susceptible to poverty by 2050.
There would also be major benefits for arctic sea ice, marine and land biodiversity, while climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth would be reduced.
- Global warming should be limited to 1.5C rather than 2C to ensure the impacts of climate change, from droughts to rising seas, are less extreme.
- By 2100, global sea rise levels would be 10cm lower with global warming of 1.5C compared to 2C.
- Coral reefs would decline by 70-90% with warming of 1.5C, compared to more than 99% with 2C.
- Human-induced warming reached approximately 1C above pre-industrial levels in 2017.
- The global temperature is currently rising by 0.2C per decade.
- If the pace of warming continues, the temperature would reach 1.5C around 2040.
- 20-40% of the global population have experienced more than 1.5C of warming in at least one season.
To limit warming to 1.5C, net emissions of carbon dioxide would need to fall by about 45% from 2010 levels by 2030, reaching "net zero" around 2050.
The IPCC says that the next few years are probably the most important in human history and the decisions we make today about climate action are critical.
The report involved 91 authors (44 citizenships, 40 countries). There were also 133 contributing authors and more than 6,000 scientific references are cited.
It considered 42,001 expert and government review comments.
The Minister with responsibility for climate change, Denis Naughten, has said he expects the report to dominate a meeting of European environment ministers in Brussels tomorrow.
He said Ireland is "looking for a significant reduction in overall transport emissions, particularly in cars and light vans, and we hope to get the support of the other member states for this tomorrow."
"€1 in every €4 that will be spent in the next decade by this government and future governments in relation to capital investment is going to be focused on climate measures and sustainable transport measures," Mr Naughten said.
"That's going to make a significant difference to our overall emissions, and we intend to work with communities right across the country to ensure that that happens."
World leaders 'need to step up'
Leading climate change activists say governments around the world must take rapid action to protect lives and livelihoods from climate change.
Former president Mary Robinson, who is an ex-UN envoy on climate change, said it was time for action, saying: "Leaders need to step up, serve their people and act immediately."
Speaking on RTÉ's Today with Sean O'Rourke, she said that Ireland is a "laggard" on climate change and needs to become a leader.
She said that huge political will and international co-operation will be needed in order to cap temperature rises at 1.5C.
Prof Jim Skea, from Imperial College London, one of the experts leading on the assessment, said the report was "unambiguous" on the difference in impacts between 1.5C and 2C of warming.
He said: "The changes that would be needed to keep global warming to 1.5C are really unprecedented in terms of their scale. We can't find any historical analogies for it.
"There are some areas we are making progress quickly enough that they are compatible with 1.5C, the example of renewables is one, where we've seen costs falling and deployment across the world.
"We need to extend this kind of progress on renewables to other areas."