It will take "transformational change" in every sector in every region of the world to keep global warming under 1.5 degrees Celsius, the world's climate scientists and governments warn.
The good news is the tools we need are tried and tested and already available to us — but they must be implemented now.
This finding comes from the latest Intergovernmental Panel on Climate Change (IPCC) report on climate change mitigation.
"We are at a crossroads," IPCC chair Hoesung Lee said.
"The decisions we make now can secure a liveable future. We have the tools and know-how required to limit warming."
Existing greenhouse gas reduction strategies can and do work, the report said, and many changes will need to be made in the energy sector by, for instance, replacing fossil-fuel-combustion technologies with alternatives that run on renewables.
The report also highlighted huge inequalities in carbon emissions — in essence, richer people emit far more carbon than poorer people.
Changing our meat-hungry, jet-setting, fossil-fuel-guzzling ways could help halve emissions by the end of the decade, the report found.
Tommy Wiedmann, professor of sustainability research at UNSW and a lead author of the "Emissions trends and drivers" chapter of the report, says "transformational change … practically in every sector and in every region" is needed if the world is to meet the aims of the Paris agreement.
Frank Jotzo, director of the Centre for Climate Economics and Policy at the Australian National University, and a lead author of the "National and sub-national policies and institutions" chapter, says the need for action now "is more urgent than it was last time the IPCC provided an assessment report in 2014".
"But the opportunity to reduce emissions at affordable costs is also greater than previously assessed," Professor Jotzo said.
This report comes from the IPCC's third working group, and follows the first working group's report on the drivers of climate change, published in August last year, and the second working group's report on climate change effects, published in February this year.
To stay under 1.5 degrees of warming above pre-industrial levels, the report said, greenhouse gas emissions must peak by 2025.
"1.5 [degrees of warming] is assessed as out of reach, unless there were immediate and deep emissions reductions in all sectors of all regions of the world, which does not appear a likely outcome," Professor Jotzo said.
Indeed, according to UN secretary-general António Guterres, the world must cut global greenhouse gas emissions by 45 per cent this decade if we are to have a chance of staying at 1.5 degrees.
"But high-emitting governments and corporations are not just turning a blind eye; they are adding fuel to the flames," Mr Guterres said.
"They are choking our planet, based on their vested interests and historic investments in fossil fuels, when cheaper, renewable solutions provide green jobs, energy security, and greater price stability."
So let's take a look at a few of the report's main findings, and what they mean for Australia's emissions reduction targets.
How have we been travelling over the past decade?
The past decade saw the highest increase in greenhouse gases in human history, peaking at more than 59 billion tonnes of carbon dioxide equivalent emitted in 2019.
Emissions dropped by about 6 per cent in 2020, driven down by the pandemic, but last year bounced back to near-2019 levels.
The report states a few specific greenhouse-gas-intensive activities grew particularly fast between 2010 and 2020, Professor Wiedmann says.
"Sales of SUVs, sports utility vehicles, went up 17 per cent. Aviation [went up] 29 per cent.
"Energy demand for cooling in residential buildings went up 40 per cent."
The report also emphasises the extreme inequality in who produces greenhouse gas emissions.
Globally, the richest 10 per cent of households contribute about 40 per cent of greenhouse gas emissions, while the bottom half contribute less than 15 per cent, Professor Wiedmann says.
Half of all emissions from aviation are caused by the top 1 per cent alone.
But there is good to go with the bad. The report found 36 countries have successfully cut greenhouse gas emissions over the past decade, Professor Wiedmann said.
The cost of renewable energy technology also dropped over the past decade, with solar, wind and batteries now 87 per cent, 55 per cent and 85 per cent cheaper than in 2010.
And the uptake of renewables more than exceeded previous expectations, Professor Wiedmann added, even over the past few months.
"Late last year, we wrote that solar and wind energy provided 7 per cent of total electricity supply globally."
That turned out to be an underestimate, with UK think tank Ember last week reporting that in 2021, 10 per cent of the world's electricity production came from solar and wind.
More renewables, along with, for instance, energy efficiency improvements are "good news and encouraging news", Professor Wiedmann said.
"But still, the change is not coming fast enough.
"The report also confirms that all the gains we made in energy efficiency in the last decade have been more than outpaced by economic growth and population growth."
So what needs to happen globally?
The report found emissions from existing and planned fossil fuel infrastructure — called committed emissions or committed carbon — would, on their own, well and truly shoot us past 1.5 degrees of warming.
In modelled scenarios that kept warming under 2 degrees, the report found the world must drastically, by 2050, roll back its use of fossil fuels and reduce:
- coal by an estimated 85 per cent
- oil by 30 per cent
- gas by 15 per cent
compared to 2019 usage.
Limiting warming doesn't only involve limiting fossil fuels — it will require the world to get to net zero by the early 2070s, says Annette Cowie, a senior principal research scientist in climate policy at the NSW Department of Primary Industries and a lead author of the "Cross-sectoral perspectives" chapter of the report.
"In order to reduce our emissions and then meet net zero, we're also going to need to deploy carbon dioxide removal strategies."
The IPCC working group assessed a dozen techniques that sequester carbon from the air, most of which were biological processes that relied on photosynthesis to store carbon in plants and soil.
Less effective options include "enhanced weathering", where crushed basalt rocks, strewn across a landscape, react with carbon dioxide in the air; and ocean fertilisation, where iron is dumped into seawater to encourage the rapid growth of photosynthetic algae.
Huge machines that scrub carbon dioxide from the air in a process called "direct air capture" also currently fall on the "less feasible" end of the spectrum, despite already operating in Iceland.
And direct air capture must be massively scaled up if it's to be useful.
A University of Melbourne report found that even if the world reaches net zero by 2050, it will still be necessary to remove 5 to 14 billion tonnes of carbon dioxide per year from the atmosphere from 2030 onwards to keep global warming below 1.5 degrees.
The plant in Iceland, which is the world's biggest, can capture and remove 4,000 metric tonnes of carbon dioxide from air each year.
Decisions about which methods of carbon removal to use will also need to consider their impact on, for instance, land use, Dr Cowie added.
"So we're going to need good governance as we introduce carbon dioxide removal strategies."
What about Australia?
In October, the Australian government promised to reach net zero emissions by 2050, with a focus on "net zero, not absolute zero emissions".
And while the latest IPCC report doesn't provide country- or region-specific assessments of mitigation policies, Professor Jotzo says, there are implications for big, sunny, windy Australia.
"Australia has plenty of opportunities right across the spectrum — renewable energy, decarbonising industry, carbon uptake on the land, you name it.
"And that includes, of course, the potential for Australia to be an exporter of zero-carbon commodities and thereby help decarbonisation in other countries."
At the moment though, climate policy in Australia is a bit of a patchwork, with no real harmonisation between federal and state policies.
"The IPCC report is very clear that the way to achieve this [climate mitigation] is through a comprehensive set of policies — not just individual policy action here and there and hoping that there will be market-driven action, but a comprehensive set of policies that complement each other," Professor Jotzo said.
So climate policy needs to be treated more like monetary policy, he added.
"All political parties agree that Australia needs sound monetary policy in order to underpin economic growth and to avoid inflation and unemployment.
"In terms of the world's authoritative stocktake of where we're heading and what we can do, [the report] very clearly shows that the opportunities are right in front of us, and that it is affordable to stay below 2 degrees."
