What does 'net zero' mean? Our climate change glossary will help you sound smart

By Laura Smith-Spark, CNN

Updated 6:05 AM ET, Thu October 28, 2021

What does 'net zero' mean? Our climate change glossary will help you sound smart

The whole world seems to be talking about the climate crisis, thanks to months of wild weather and new science showing that we need to act quicker than we previously thought to avoid the worst consequences.

As leaders prepare to meet in Glasgow, Scotland, next month for crunch talks, they'll be using a lot of technical lingo. The terminology isn't particularly communicative and can be daunting.Even the name of the summit -- COP26 -- sounds more like a bad police drama than a climate event. (First pointer: COP is short for Conference of the Parties to the UN Convention on Climate Change. It convenes global leaders, scientists and negotiators on climate, and usually takes place annually. The "26" means Glasgow will be the 26th meeting.)Nationally Determined Contributions -- or NDCs -- is a term used by the UN for each country's individual national plan to slash greenhouse gas emissions. In the 2015 Paris Agreement, which nearly the whole world signed on to, countries were given the freedom to determine themselves how they would go about meeting the agreement's key targets to slow global warming. NDCs are supposed to be updated every five years and submitted to the UN, the idea being that each country's ambition will grow over time. Dozens of countries have failed to submit their updates ahead of COP26.Smokestacks at Skoda's main foundry in Pilsen, then part ofCzechoslovakia, on August 29, 1938.This usually refers to average concentration of carbon dioxide in the atmosphere before the Industrial Revolution, which started in the late 18th century. CO2 levels are estimated to have been around 280 parts per million at that time. By 2020, that concentration had risen to 412.5 parts per million, according to US government figures. Scientists also talk about pre-industrial levels for average temperatures, using the period 1850-1900 to determine how hot or cold the Earth was before humans began emitting greenhouse gases at larger volumes, like those we see today.A key goal of COP26 President Alok Sharma, a British MP, is "keeping 1.5 alive," which refers to a target to keep average global temperature rise to 1.5 degrees Celsius above pre-industrial levels. It's a target that some fossil fuel-producing countries have resisted, and scientists have warned of significantly worse impacts if this threshold is breached. What is COP26? How the pivotal UN conference could avert global climate 'catastrophe'The countries that signed the Paris Agreement in 2015 agreed to limit the increase in global temperatures to well below 2 degrees above pre-industrial levels, but preferably to 1.5 degrees. However, an analysis released last month by watchdog Climate Action Tracker (CAT) found that not a single major economy -- including the entire G20 -- had a climate plan that meets its obligations under Paris.The United Nations' Intergovernmental Panel on Climate Change (IPCC) said in its latest state-of-the-science report that the world has already warmed by 1.1 degrees above than pre-industrial levels, and is now hurtling fast toward 1.5 degrees. More than 10 years ago, at COP16 in Cancún, Mexico, the developed world agreed to transfer money to developing countries to help them limit or reduce their greenhouse gas emissions and adapt to the climate crisis. They set up the Green Climate Fund (GCF) to facilitate some of this transfer, but countries and donors can send money through any means they like. The money was supposed to build up and reach $100 billion annually by 2020, and that commitment was reaffirmed in the Paris Agreement. This money is often referred to broadly as "climate finance." But the 2020 target was missed, and filling the gap is high on the agenda for the talks in Glasgow. Developing nations, particularly those in the Global South, which are most vulnerable to the effects of climate change, argue that industrialized nations are historically more responsible for climate change and must do more to fund changes to help developing nations adapt.US President Joe Biden pledged to double the US' existing contribution plans, including money for the Green Climate Fund, in a speech at the UN General Assembly in September. Some critics say he should pledge more to make up for the Trump years, when no money was paid into the fund. Vehicles stranded by high water in the Bronx borough of New York City after Hurricane Ida on September 2, 2021. Adaptation refers to the way humans can change their lives to better cope with the impacts of climate change. These might include building early warning systems for floods or barriers to defend against rising sea levels, for example. In some places where rainfall is decreasing, planting drought-resistant varieties of crops can help ensure communities have enough food to eat.Put simply, this refers to how humans can reduce greenhouse gas emissions, or remove them from the atmosphere, to ease the consequences of climate change.Examples include using fossil fuels like coal, oil and gas more efficiently for industrial processes, switching from coal and gas to renewable energy sources such as wind or solar power for electricity, choosing public transport to commute over private vehicles that run on gasoline, and expanding forests and other means of absorbing carbon.You might hear leaders talking about the end of "unabated" coal. Unabated coal refers to coal burned in power stations where no action -- or "abatement" -- is taken to reduce the greenhouse gases emitted by its use. In short, this creates a loophole for some continued coal power in a net zero world, if the greenhouse gases it emits are captured. Very few coal plants in the world, however, are using abatement technologies, and transitioning to renewables is often more economically feasible in the long term than employing them.In its 2021 report "Net Zero by 2050," the International Energy Agency states that a "rapid shift" will be needed away from fossil fuels to achieve the goal, requiring steps such as "phasing out all unabated coal and oil power plants by 2040." A customer prepares to charge a Tesla electric car at a supermarket in north London. That's electric vehicles to you and me. As electricity generated by renewables, like wind and solar, becomes more available, people are expected to start buying electric vehicles in greater numbers, especially as they become more affordable. That will mean fewer cars powered by oil on the roads, which is another topic on the agenda for COP26.There may also be references to PHEVs -- those are plug-in hybrid electric vehicles, which are mostly powered by a battery charged from an electrical source but also have a hybrid internal combustion engine to allow travel over longer distances. This refers to the idea that the drastic changes needed to combat climate change should be fair to everyone. As environmental campaign group Greenpeace says: "Put simply, a just transition is about moving to an environmentally sustainable economy (that's the 'transition' part) without leaving workers in polluting industries behind. It aims to support good quality jobs and decent livelihoods when polluting industries decline and others expand, creating a fairer and more equal society -- that's what makes it 'just.'"Biodiversity refers to all the Earth's living systems, on land and in the sea. The UN's Global Biodiversity Outlook report published just over a year ago warned that the accelerating climate crisis was worsening the outlook for biodiversity -- that can mean all the trees, plants and animals in a forest, or all the fish and coral in a reef. "Biodiversity is declining at an unprecedented rate, and the pressures driving this decline are intensifying," it said. Challenges include habitat loss and degradation, mass extinction of species, declining wetlands, and pollution by plastic and pesticides. Earlier this year, the G7 countries -- the seven largest advanced economies -- agreed to conserve 30% of land and sea in their nations to protect biodiversity, a pledge they hope will be adopted by more countries at COP26. At COP24 in 2018, world leaders agreed to come up with a set of rules meant to help curb global warming -- the so-called Paris Rulebook -- which is supposed to put into motion the Paris Agreement. But they did not resolve a critical but complicated issue involving how countries trade and account for certain types of pollution.