Climate explained: how much of the world’s energy comes from fossil fuels and could we replace it all with renewables?


Shutterstock/Tsetso Photo

Robert McLachlan, Massey University


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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


How are fossil fuels formed, why do they release carbon dioxide and how much of the world’s energy do they provide? And what are the renewable energy sources that could replace fossil fuels?

Fossil fuels were formed over millions of years from the remains of plants and animals trapped in sediments and then transformed by heat and pressure.

Most coal was formed in the Carboniferous Period (360–300 million years ago), an age of amphibians and vast swampy forests. Fossilisation of trees moved enormous amounts of carbon from the air to underground, leading to a decline in atmospheric carbon dioxide (CO₂) levels — enough to bring the Earth close to a completely frozen state.

This change in the climate, combined with the evolution of fungi that could digest dead wood and release its carbon back into the air, brought the coal-forming period to an end.

Oil and natural gas (methane, CH₄) were formed similarly, not from trees but from ocean plankton, and over a longer period. New Zealand’s Maui oil field is relatively young, dating from the Eocene, some 50 million years ago.




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Burning buried sunshine

When fossil fuels are burnt, their carbon reacts with oxygen to form carbon dioxide. The energy originally provided by the Sun, stored in chemical bonds for millions of years, is released and the carbon returns to the air. A simple example is the burning of natural gas: one molecule of methane and two of oxygen combine to produce carbon dioxide and water.

CH₄ + 2 O₂ → CO₂ + 2 H₂O

Burning a kilogram of natural gas releases 15kWh of energy in the form of infrared radiation (radiant heat). This is a sizeable amount.

To stop continuously worsening climate change, we need to stop burning fossil fuels for energy. That’s a tall order, because fossil fuels provide 84% of all the energy used by human civilisation. (New Zealand is less reliant on fossil fuels, at 65%.)

Wind turbines on farm land in New Zealand
Wind energy is one of the renewable sources with the capacity to scale up.
Shutterstock/YIUCHEUNG

There are many possible sources of renewable or low-carbon energy: nuclear, hydropower, wind, solar, geothermal, biomass (burning plants for energy) and biofuel (making liquid or gaseous fuels out of plants). A handful of tidal power stations are in operation, and experiments are under way with wave and ocean current generation.

But, among these, the only two with the capacity to scale up to the staggering amount of energy we use are wind and solar. Despite impressive growth (doubling in less than five years), wind provides only 2.2% of all energy, and solar 1.1%.

The renewables transition

One saving grace, which suggests a complete transformation to renewable energy may be possible, is that a lot of the energy from fossil fuels is wasted.

First, extraction, refining and transport of fossil fuels accounts for 12% of all energy use. Second, fossil fuels are often burnt in very inefficient ways, for example in internal combustion engines in cars. A world based on renewable energy would need half as much energy in the first place.

The potential solar and wind resource is enormous, and costs have fallen rapidly. Some have argued we could transition to fully renewable energy, including transmission lines and energy storage as well as fully synthetic liquid fuels, by 2050.

One scenario sees New Zealand building 20GW of solar and 9GW of wind power. That’s not unreasonable — Australia has built that much in five years. We should hurry. Renewable power plants take time to build and industries take time to scale up.

Other factors to consider

Switching to renewable energy solves the problems of fuel and climate change, but not those of escalating resource use. Building a whole new energy system takes a lot of material, some of it rare and difficult to extract. Unlike burnt fuel, metal can be recycled, but that won’t help while building a new system for the first time.

Research concluded that although some metals are scarce (particularly cobalt, cadmium, nickel, gold and silver), “a fully renewable energy system is unlikely to deplete metal reserves and resources up to 2050”. There are also opportunities to substitute more common materials, at some loss of efficiency.

Engineers working on a wind turbine
Building a new system will require energy and resources.
Shutterstock/Jacques Tarnero

But many metals are highly localised. Half the world’s cobalt reserves are in the Democratic Republic of Congo, half the lithium is in Chile, and 70% of rare earths, used in wind turbines and electric motors, are in China.

Wasteful consumption is another issue. New technologies (robots, drones, internet) and economic growth lead to increased use of energy and resources. Rich people use a disproportionate amount of energy and model excessive consumption and waste others aspire to, including the emerging rich in developing countries.




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Research analysing household-level emissions across European countries found the top 1% of the population with the highest carbon footprints produced 55 tonnes of CO₂-equivalent emissions each, compared to a European median of 10 tonnes.

Scientists have warned about consumption by the affluent and there is vigorous debate about how to reduce it while preserving a stable society.

One way of turning these questions around is to start from the bottom and ask: what is the minimum energy required for basic human needs?

One study considered “decent living” to include comfortable housing, enough food and water, 10,000km of travel a year, education, healthcare and telecommunications for everyone on Earth — clearly not something we have managed to achieve so far. It found this would need about 4,000kWh of energy per person per year, less than a tenth of what New Zealanders currently use, and an amount easily supplied by renewable energy.

All that carbon under the ground was energy ripe for the picking. We picked it. But now it is time to stop.The Conversation

Robert McLachlan, Professor in Applied Mathematics, Massey University

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

Saving these family-focused lizards may mean moving them to new homes. But that’s not as simple as it sounds


Holly Bradley, Author provided

Holly Bradley, Curtin University; Bill Bateman, Curtin University, and Darryl Fogarty, Indigenous KnowledgeAm I not pretty enough? This article is part of The Conversation’s series introducing you to unloved Australian animals that need our help.


Spiny-tailed skinks (Egernia stokesii badia), known as meelyu in the local Badimia language in Western Australia, are highly social lizards that live together in family groups — an uncommon trait among reptiles.

They’re culturally significant to the Badimia people but habitat degradation and mining has put them under threat of extinction.

These sturdy, mottled lizards — which live in colonies in the logs of fallen trees and branches — are a candidate for what researchers call “mitigation translocation”.

That’s where wildlife are relocated away from high-risk areas (such as those cleared for urban development or mining) to lower risk areas.

It might sound simple. But research shows these mitigation translocation decisions are often made on an ad hoc basis, without a long-term strategic plan in place.

Example of the range in individual size/age occupying the same permanent log pile structure within the Mid West region of Western Australia.
Holly Bradley, Author provided

Not enough pre-planning or follow-up

There has been much research into assisted relocation of larger, charismatic mammals and birds. But other animals, such as reptiles with a less positive social image, have been less widely studied.

Our recent research has found there is often little pre-planning or follow-up to monitor success of mitigation translocations, even though reptile mitigation translocations do take place, sometimes on a large scale.

In fact, fewer than 25% of mitigation translocations worldwide actually result in long-term self-sustaining populations.

Mitigation translocation methods are also not being improved. Fewer than half of published mitigation translocation studies have explicitly compared or tested different management techniques.

Mitigation translocation studies also rarely consider long-term implications such as how relocated animals can impact the site to which they are moved — for example, if the ecosystem has limited capacity to support the relocated animals.

But it’s not just about ecosystem benefits. Preservation of species such as meelyu also has cultural benefits — but mitigation translocation can only be part of the solution if it’s done strategically.




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The meelyu: a totem species

As part of Holly Bradley’s research into understanding how to protect meelyu from further loss in numbers, she had the privilege to meet with Badimia Indigenous elder, Darryl Fogarty, who identified meelyu as his family’s totem.

Totemic species can represent a person’s connection to their nation, clan or family group.

The meelyu or Western Spiny-tailed Skink is significant to the Badimia people and require translocation as part of mine site restoration and mitigation of population loss.
Holly Bradley, Author provided

Unfortunately, Darryl Fogarty cannot remember the last time he saw the larger meelyu in the area. The introduction of European land management and feral species into Western Australia has upset the ecosystem balance — and this also has cultural consequences.

Preserving totemic fauna in their historic range can be a critical component of spiritual connection to the land for Indigenous groups in Australia.

In the past, this spiritual accountability for the stewardship of a totem has helped protect species over the long term, with this responsibility passed down between generations.

Before European colonisation, this traditional practice helped to preserve biodiversity and maintain an abundance of food supplies.

A strategic approach to future meelyu relocations from areas of active mining is crucial to prevent further population losses — for both ecological and cultural reasons.

Good mitigation translocation design

If we are to use mitigation translocation to shore up their numbers, we need effective strategies in place to boost the chance it will actually help the meelyu.

Good mitigation translocation design includes factors such as:

  • selecting a good site and understanding properly whether it can support new wildlife populations
  • having a good understanding of the animal’s ecological needs and how they fit with the environment to which they’re moving
  • using the right methods of release for the circumstances. For example, is it better to use a soft release method, where an individual animal is gradually acclimatised to its new environs over time? Or a hard release method, where the animal is simply set free in its new area?
  • having a good understanding of the cultural factors involved.

A holistic approach

A holistic approach to land management and restoration practice considers both cultural and ecological significance.

It supports the protection and return of healthy, functioning ecosystems — as well as community well-being and connection to nature.

Mitigation translocation could have a role to play in protection of culturally significant wildlife like the meelyu, but only when it’s well planned, holistic and part of a long term strategy.




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The Conversation


Holly Bradley, PhD candidate, Curtin University; Bill Bateman, Associate professor, Curtin University, and Darryl Fogarty, Badimia Elder, Indigenous Knowledge

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

How much will our oceans warm and cause sea levels to rise this century? We’ve just improved our estimate


Jakob Weis, University of Tasmania, Author provided

Kewei Lyu, CSIRO; John Church, UNSW, and Xuebin Zhang, CSIROKnowing how much sea levels are likely to rise during this century is vital to our understanding of future climate change, but previous estimates have generated wide ranges of uncertainty. In our research, published today in Nature Climate Change, we provide an improved estimate of how much our oceans are going to warm and its contribution to sea level rise, with the help of 15 years’ worth of measurements collected by a global array of autonomous underwater sampling floats.

Our analysis shows that without dramatic reductions in greenhouse gas emissions, by the end of this century the upper 2,000 metres of the ocean is likely to warm by 11-15 times the amount of warming observed during 2005-19. Water expands as it gets warmer, so this warming will cause sea levels to rise by 17-26 centimetres. This is about one-third of the total projected rise, alongside contributions from deep ocean warming, and melting of glaciers and polar ice sheets.

Ocean warming is a direct consequence of rising greenhouse gas concentrations in the atmosphere as a result of our burning of fossil fuels. This results in an imbalance between the energy arriving from the Sun, and the energy radiated out into space. About 90% of the excess heat energy in the climate system over the past 50 years is stored in the ocean, and only about 1% in the warming atmosphere.

Warming oceans cause sea levels to rise, both directly via heat expansion, and indirectly through melting of ice shelves. Warming oceans also affect marine ecosystems, for example through coral bleaching, and play a role in weather events such as the formation of tropical cyclones.

Systematic observations of ocean temperatures began in the 19th century, but it was only in the second half of the 20th century that enough observations were made to measure ocean heat content consistently around the globe.

Since the 1970s these observations indicate an increase in ocean heat content. But these measurements have significant uncertainties because the observations have been relatively sparse, particularly in the southern hemisphere and at depths below 700m.

To improve this situation, the Argo project has deployed a fleet of autonomous profiling floats to collect data from around the world. Since the early 2000s, they have measured temperatures in the upper 2,000m of the oceans, and sent the data via satellite to analysis centres around the world.

These data are of uniform high quality and cover the vast majority of the open oceans. As a result, we have been able to calculate a much better estimate of the amount of heat accumulating in the world’s oceans.

Global distribution of Argo floats.
Argo project

The global ocean heat content continued to increase unabated during the temporary slowdown in global surface warming in the beginning of this century. This is because ocean warming is less affected than surface warming by natural yearly fluctuations in climate.




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Current observations, future warming

To estimate future ocean warming, we need to take the Argo observations as a basis and then use climate models to project them into the future. But to do that, we need to know which models are in closest agreement with new, more accurate direct measurements of ocean heat provided by the Argo data.

The latest climate models, used in last month’s landmark report by the Intergovernmental Panel on Climate Change, all show ocean warming over the period of available Argo observations, and they project that warming will continue in the future, albeit with a wide range of uncertainties.

Ocean warming magnitudes from latest climate model simulations and Argo observations.




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By comparing the Argo temperature data for 2005-19 with the simulations generated by models for that period, we used a statistical approach called “emergent constraint” to reduce uncertainties in model future projections, based on information about the ocean warming we know has already occurred. These constrained projections then provided an improved estimate of how much heat energy will accumulate in the oceans by the end of the century.

By 2081–2100, under a scenario in which global greenhouse emissions continue on their current high trajectory, we found the upper 2,000m of the ocean is likely to warm by 11-15 times the amount of warming observed during 2005-19. This corresponds to 17–26cm of sea level rise from ocean thermal expansion.

Climate models can also make predictions based on a range of different future greenhouse gas emissions. Strong emissions reductions, consistent with bringing surface global warming to within about 2℃ of pre-industrial temperatures, would reduce the projected warming in the upper 2,000m of the ocean by about half — that is, between five and nine times the ocean warming already seen in 2005-19.

This would equate to 8-14cm of sea level rise due to thermal expansion. Of course, reducing emissions so as to hit the more ambitious Paris target of 1.5℃ surface warming would reduce these impacts even further.

Other factors linked to sea levels

There are several other factors that will also drive up sea levels, besides the heat influx into the upper oceans investigated by our research. There is also warming of the deep ocean below 2,000m, which is still under-sampled in the current observing system, as well as the effects of melting from glaciers and polar ice sheets.

This indicates that even with strong policy action to reduce greenhouse gas emissions, the oceans will continue to warm and sea levels will continue to rise well after surface warming is stabilised, but at a much reduced rate, making it easier to adapt to the remaining changes. Cutting greenhouse gas emissions earlier rather than later will be more effective at slowing ocean warming and sea level rise.




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Our improved projection is founded on a network of ocean observations that are far more extensive and reliable than anything available before. Sustaining the ocean observing system into the future, and extending it to the deep ocean and to areas not covered by the present Argo program, will allow us to make more reliable climate projections in the future.The Conversation

Kewei Lyu, Postdoctoral Researcher in Ocean and Climate, CSIRO; John Church, Chair Professor, Climate Change Research Centre, UNSW, and Xuebin Zhang, Principal Research Scientist, CSIRO

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