Feed aggregator
Asian nations make plastic oceans promise
NAB, CEFC extend green loan scheme as farmers flock to solar, efficiency
Support for Low Emissions Target ahead of Finkel report release
What is a pre-industrial climate and why does it matter?
Over the past few days there has been a lot of talk about the Paris climate agreement, from which the United States is planning to withdraw. Although this is a setback, there is still near-complete consensus from the world’s governments that a strong effort to tackle climate change is needed.
The Paris Agreement aims to limit global warming relative to a pre-industrial baseline. Its precise commitment is:
Holding the increase in the global average temperature to well below 2℃ above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5℃ above pre-industrial levels, recognising that this would significantly reduce the risks and impacts of climate change.
But this begs the question: what are “pre-industrial levels”?
Clearly, if we’re aiming to limit global warming to 1.5℃ or 2℃ above a certain point, we need a common understanding of what we’re working from. But the Paris Agreement doesn’t provide a definition.
This becomes key as governments expect climate scientists to coherently compare different plans to reach their Paris targets. It’s crucial to be clear on what researchers mean when we say “pre-industrial”, and what assumptions our projections are based on.
Of course, as the chart below shows, no matter which baseline we use it’s clear there’s been a drastic rise in global temperature over the last century.
![](https://cdn.theconversation.com/files/172364/width754/file-20170606-16888-1up5870.png)
The Industrial Revolution began in the late 1700s in Britain, and spread around the world. But this only marked the beginning of a gradual rise in our greenhouse gas emissions. Various studies have found climate change signals appearing on a global scale as early as the 1830s, or as recently as the 1930s.
Besides the evolving and increasing human influence on the climate, we also know that plenty of other natural factors can affect Earth’s temperature. This natural variability in the climate makes it harder to determine a single precise pre-industrial baseline.
Scientists separate these natural influences on the climate into two groups: internal and external forcings.
Internal forcings transfer heat between different parts of Earth’s climate system. The El Niño-Southern Oscillation, for example, moves heat between the atmosphere and the ocean, causing year-to-year variations in global average surface temperatures of about 0.2℃. Similar variations also happen on decadal timescales, which are associated with slower energy transfers and longer variations in Earth’s temperature.
External forcings come from outside Earth’s climate system to influence global temperature. One example of an external forcing is volcanic eruptions, which send particles into the upper atmosphere. This prevents energy from the Sun reaching Earth’s surface, and leads to a temporary cooling.
Another external influence on Earth’s climate is the variability in the amount of energy the Sun emits.
The Sun’s total energy output varies on multiple cycles and is related to the number of sunspots, with slightly higher temperatures when there are more sunspots, and vice versa.
Earth has experienced extended periods of cooling due to more frequent explosive volcanic eruptions and periods of few sunspots – such as during the “Little Ice Age” which lasted roughly from 1300 to the 1800s.
![](https://cdn.theconversation.com/files/172224/width754/file-20170605-31050-llehtt.png)
All of these factors mean that Earth’s climate can vary quite substantially even without human interference.
It also means that if we choose a pre-industrial baseline when there was low solar activity, like the late 1600s, or in a period of high volcanic activity, like the 1810s or the 1880s, then we would have a lower reference point and we would pass through 1.5℃ or 2℃ sooner.
A challenge not only for scientistsAt the moment there is a drive among the climate science community to better understand the impacts of 1.5℃ of global warming. The Intergovernmental Panel on Climate Change will deliver a special report on 1.5℃ next year.
But scientists are defining “pre-industrial” or “natural” climate in different ways. Some work from the beginning of global temperature records in the late 19th century, while others use climate model simulations that exclude human influences over a more recent period. One recent study suggested that the best baseline might be 1720-1800.
These different definitions make it harder to synthesise the results from individual studies, which is vital to informing decision-making.
This will have to be a consideration in the writing of the IPCC’s report, as policymakers will need to easily compare impacts at different levels of global warming.
There is no definitive way to determine the best “pre-industrial” reference point. An alternative might be to avoid the pre-industrial baseline altogether, and instead set targets from more recent periods, when we have a better grasp of what the global climate looked like.
You can read more about defining a pre-industrial climate here and here.
![The Conversation](https://counter.theconversation.edu.au/content/78601/count.gif)
Andrew King receives funding from the ARC Centre of Excellence for Climate System Science.
Ben Henley receives funding from an ARC Linkage Project and is an associate investigator with the ARC Centre of Excellence for Climate System Science.
Ed Hawkins receives funding from the UK's Natural Environment Research Council and National Centre for Atmospheric Science.
Australia's carbon emissions rise in off-season for first time in a decade
Exclusive: On the eve of the long-awaited Finkel review, analysis shows Australia’s emissions rose sharply in the first quarter of 2017
Australia’s carbon emissions jumped at the start of 2017, the first time they have risen in the first few months of a year for more than a decade, according to projections produced exclusively for the Guardian.
Emissions in the first three months of the year normally drop compared with the previous quarter, driven by seasonal factors and holidays. But in something not seen in since 2005, emissions rose in the first quarter of 2017 compared with the last quarter of 2016 by 1.54m tonnes of CO2, according to the study by consultants NDEVR Environmental. The rise was driven by increases in emissions from electricity generation.
Continue reading...In Utah, federal land opponent reverses stance on drilling near Zion national park
In a change of tone, Utah governor Gary Herbert has backpedaled and asked the federal government not to allow oil and gas drilling around the famous park
When Utah governor Gary Herbert changed his mind last week and decided oil and gas companies should not be allowed to drill near Zion national park, it seemed like a remarkable change of tone.
The Republican has been a staunch advocate for rolling back public land protections and had earlier endorsed the idea of drilling near the 229 sq mile park. In February, he signed a resolution urging Donald Trump to rescind national monument status for the 1.3m acres known as Bears Ears in south-eastern Utah. Doing so would allow expansion of current leases for oil and gas development and grazing.
Continue reading...Thank you: with your help, we raised $50,000 to cover America's public lands
In just 31 hours, Guardian US exceeded its target to support a new series on the threat to America’s public lands. We’d like to thank you for your generosity
We would like to extend a huge thank you to the more than 1,000 Guardian readers who made contributions to support This Land is Your Land, our series on the threat to America’s public lands. We launched our fundraising campaign on Monday morning, and hit our $50,000 goal at 1pm Tuesday, just 31 hours after the launch. When this article was published we had exceeded our goal by 20%, with $60,166 pledged. More than 1,000 readers have contributed.
Continue reading...Discovery of 300,000-year-old fossils rewrites origins of our species
Winds of change: gusts across Europe help set renewable power record
Nuclear, wind and solar power in UK generate more electricity than gas and coal combined for first time ever
The windy weather across Europe in the past 24 hours may have been a curse for summer picnics, but it has set records for renewable power.
Related: 'Spectacular' drop in renewable energy costs leads to record global boost
Continue reading...'First of our kind' found in Morocco
Whiskey, with a peacock chaser: bird smashes up US liquor store – video
A peacock which found its way into a Californian liquor store causes hundreds of dollars of damage before an animal control officer and the store manager are able to capture it
Continue reading...How can humans and elephants better coexist?
The human-elephant conflict plays a huge role in the rapid decline elephant numbers. A panel of experts share ideas on how to mitigate this problem
We need conservation (not just fighting the illegal wildlife trade which has captured the limelight more recently) to be far higher up the political agenda. For example, we in the UK could be much more effectively linking overseas aid (budget of £12bn this year) to poverty relief, sustainable development and environmental protection, ecosystem services and conservation priorities. Will Travers, president, Born Free Foundation
Continue reading...Electric cars accelerate past 2m mark globally
China, US and Europe accounted for more than 90% of electric vehicle sales last year with decreasing costs driving demand
The number of electric cars in the world accelerated past the 2m barrier last year, as prices fell and manufacturers launched new models.
The number of battery-powered vehicles numbered just hundreds globally in 2005 and passed the 1m milestone in 2015, but sales jumped 60% in 2016.
Rare US floods to become the norm if emissions aren't cut, study warns
- Princeton-Rutgers study finds sharp increase in risk of frequent deluges
- ‘Many cities are behind the eight-ball in terms of preparing for flooding’
US coastal areas are set to be deluged by far more frequent and severe flooding events if greenhouse gas emissions aren’t slashed, with rare floods becoming the norm for places such as New York City, Seattle and San Diego, new research has found.
Related: Climate change progress at Trump's EPA is grinding to a halt, workers reveal
Continue reading...A tax on meat
Paris pollution victim sues France for bad air
A field guide to the spiders of Australia
Antarctic Halley base waits on ice behaviour
British ice station on the move
Demand for elephant skin, trunk and penis drives rapid rise in poaching in Myanmar
A growth in demand for elephant parts to be used in traditional medicine in Asia means the number of elephants being killed in Myanmar is rising
Case files and laminated photos of poachers spill out of captain Than Naing’s folder. As the chief of police in Okekan township, one of Myanmar’s recent poaching hotspots, he is trying to track down the men who have killed at least three elephants in the area over the past year. So far, he has arrested 11 people suspected of having assisted the poachers. Meanwhile the poachers themselves remain at large.
“These are the two men who we believe killed one of the elephants,” he says, pointing to two photos. “They are still on the run.”
Continue reading...