Climate Explained: what Earth would be like if we hadn’t pumped greenhouse gases into the atmosphere



OSORIOartist/Shutterstock

Laura Revell, University of Canterbury


CC BY-ND

Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.

If you have a question you’d like an expert to answer, please send it to climate.change@stuff.co.nz

This week, Climate Explained answers two similar questions.

If humans had not contributed to greenhouses gases in any way at all, what would the global temperature be today, compared to the 1800s before industrialisation?

and

My question is what happens when all the greenhouse gases are eliminated? What keeps the planet from cooling past a point that is good?

Earth’s atmosphere is a remarkably thin layer of gases that sustain life.

The diameter of Earth is 12,742km and the atmosphere is about 100km thick. If you took a model globe and wrapped it up, a single sheet of tissue paper would represent the thickness of the atmosphere.

The gases that make up Earth’s atmosphere are mostly nitrogen and oxygen, and small quantities of trace gases such as argon, neon, helium, the protective ozone layer and various greenhouse gases – so named because they trap heat emitted by Earth.

The most abundant greenhouse gas in Earth’s atmosphere is water vapour – and it is this gas that provides the natural greenhouse effect. Without this and the naturally occurring quantities of other greenhouse gases, Earth would be about 33℃ colder and uninhabitable to life as we know it.

Changing Earth’s atmosphere

Since pre-industrial times, human activities have led to the accumulation of greenhouse gases such as carbon dioxide, methane and nitrous oxide in the atmosphere. The concentration of atmospheric carbon dioxide has risen from about 280 parts per million (ppm) before the first industrial revolution some 250 years ago, to a new high since records began of just over 417ppm. As a result of continued increases, the global average temperature has climbed by just over 1℃ since pre-industrial times.




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While these long-lived greenhouse gases have raised Earth’s average surface temperature, human activities have altered atmospheric composition in other ways as well. Particulate matter in the atmosphere, such as soot and dust, can cause health problems and degrades air quality in many industrialised and urban regions.

Particulate matter can partially offset greenhouse gas warming, but its climate effects depend on its composition and geographical distribution. Climate in the southern hemisphere has also been affected by chlorofluorocarbons (CFCs), which led to the development of the Antarctic ozone hole.

If people had not altered the composition of the atmosphere at all through emitting greenhouse gases, particulate matter and ozone-destroying CFCs, we would expect the global average temperature today to be similar to the pre-industrial period – although some short-term variation associated with the Sun, volcanic eruptions and internal variability would still have occurred.




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In a world that is about 1℃ warmer than during pre-industrial times, New Zealand is already facing the environmental and economic costs associated with climate change. The former head of the UN Framework Convention on Climate Change (UNFCCC), Christiana Figueres, argues that with trillions of dollars being spent around the world in economic stimulus packages following the COVID-19 pandemic, we need strong commitments to a low-carbon future if the world is to limit warming to 1.5℃ above pre-industrial levels.

What needs to happen

Greenhouse gases have long lifetimes – about a decade for methane and hundreds to thousands of years for carbon dioxide. We will need to reduce emissions aggressively over a sustained period, until their abundance in the atmosphere starts to decline.

When New Zealand entered the Level 4 coronavirus lockdown in March 2020, almost two weeks passed (the incubation period of the virus) before the number of new cases started to decline. Waiting for atmospheric carbon dioxide concentrations to decrease, even while we reduce emissions, will be similar, except we’ll be waiting for decades.

It is very unlikely that we could ever reduce greenhouse gas concentrations to the point that it becomes dangerous for life as we know it. Doing so would involve overcoming the natural greenhouse effect.

Recent research into greenhouse gas emission scenarios provides guidance on what will need to happen to stabilise Earth’s temperature at 1.5℃ above pre-industrial levels. A rapid transition away from fossil fuels toward low-carbon energy is imperative; some form of carbon dioxide capture to remove it from the atmosphere may also be necessary.

Short-term and scattered climate policy will not be sufficient to support the transitions we need, and achieving 1.5℃ will not be possible as long as global inequalities remain high.The Conversation

Laura Revell, Senior Lecturer in Environmental Physics, University of Canterbury

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Australia has failed miserably on energy efficiency – and government figures hide the truth



Dave Hunt/AAP

Hugh Saddler, Australian National University

Amid the urgent need to slow climate change by cutting greenhouse gas emissions, energy efficiency makes sense. But as Australia’s chief scientist Alan Finkel last week warned, we’re not “anywhere close to having that nailed”.

Energy efficiency means using less energy to achieve the same outcomes. It’s the cheapest way to cut greenhouse gas emissions and achieve our climate goals. Improving energy efficiency is also vital to achieving so-called “energy productivity” – getting more economic output, using the same or less energy.

But Australia’s national energy productivity plan, agreed by the nation’s energy ministers in 2015, has gone nowhere.

It set a goal of a 40% improvement in energy productivity by 2030. But my analysis, based on the most recent official data, shows that in the three years to 2017-18, energy productivity increased by a mere 1.1%.

Clearly, there is much work to do. So let’s take a look at the problem and the potential solutions.

Energy efficiency reduces power bills for consumers.
Julian Smith/AAP

Energy efficiency: a low-hanging fruit

Better energy efficiency lowers electricity bills, makes businesses more competitive and helps manage energy demand. Of course, it also means less greenhouse gas emissions, because fewer fossil fuels are burnt for energy.

Business, unions and green groups recognise the benefits. Last month they joined forces to call for a sustainable COVID-19 economic recovery, with energy efficiency at the core, saying:

In Australia, a major drive to improve the energy efficiency of buildings and industry could deliver over 120,000 job-years of employment […] Useful upgrades could be made across Australia’s private and public housing; commercial, community and government buildings; and industrial facilities.

The group said improvements could include:

  • more efficient and controllable appliances and equipment, especially for heating and cooling
  • improved shading and thermal envelopes (improving the way a building’s walls, ceiling and floors prevent heat transfer)
  • smart meters to measure energy use
  • distributed energy generation and storage, such as wind and solar backed by batteries
  • fuel switching (replacing inefficient fuels with cleaner and economical alternatives)
  • equipment, training and advice for better energy management.



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The International Energy Agency (IEA) has suggested other measures for industry and manufacturing, such as:

  • installing more efficient electric motors
  • switching from gas to electric heat pumps
  • more waste and material recycling.

And in transport, the IEA suggests incentives to get older, less efficient cars off the roads and encourage the uptake of electric vehicles.

Residential buildings offer big opportunities for energy efficiency improvements.
Brendan Esposito/AAP

Governments’ sleight of hand

In 2018 the IEA observed:

the power sector will be at the heart of Australia’s energy system
transformation […] International best practice suggests that both energy efficiency and renewable energy are key drivers of the energy transition.

Since then, renewable energy’s share of the electricity mix has increased. But energy productivity has stalled.

To understand how, we must define a few key terms.

Primary energy refers to energy extracted from the environment, such as coal, crude oil, and electrical energy collected by a wind turbine or solar panel.

Final energy is the energy supplied to a consumer, such as electricity delivered to homes or fuel pumped at a petrol station.




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A lot of energy is lost in the process of turning extracted primary fuels into ready-to-use fuels for consumers. For example at coal-fired power stations, on average, one-third of the energy supplied by burning coal is converted to electricity. The remainder is lost as waste heat.

Until 2015, Australia and most other countries used final energy as a measure of how rapidly energy efficiency was improving. But the national productivity plan instead set goals around primary energy productivity – aiming to increase it by 40% between 2015 and 2030.

This has made it possible for governments to hide how badly Australia is travelling on improving energy efficiency. I analysed national accounts figures and energy statistics, to produce the below table. It reveals the governments’ sleight of hand.

Over the three years from 2014-15 to 2017-18, final energy productivity increased by only 1.1%, whereas primary energy productivity increased by 3.5%.

The reduced primary energy consumption is mostly due to a large increase in wind and solar generation. The efficiency of energy used by final consumers has scarcely changed.

A sustainable future

The lack of progress on energy productivity is not surprising, given governments have shown very little interest in the issue.

As Finkel noted in his address, Australia’s energy productivity plan is absent from the list of national climate and energy policies. The plan’s 2019 annual report has not been released. And those released since 2015 have not monitored progress in energy productivity.

What’s more, the plan makes no mention of previous similar agreements, in 2004 and 2009, to accelerate energy efficiency with regulation and financial incentives. Since 2013, almost all Commonwealth programs supporting those agreements have been de-funded or abolished, and many state programs have also been cut back.




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The IEA’s sustainable recovery plan, released last week, outlined what a sustainable global economic recovery might look like. In particular, it said better energy efficiency and switching to more efficient electric technologies will deliver triple benefits: increased employment, a more productive economy and lower greenhouse gas emissions.

In this carbon-constrained world, relatively easy and cheap opportunities such as energy efficiency must be seized. And as Australia spends to get its post-pandemic economy back on track, now is the time to act.The Conversation

Hugh Saddler, Honorary Associate Professor, Centre for Climate Economics and Policy, Australian National University

This article is republished from The Conversation under a Creative Commons license. Read the original article.