It will be DECADES before reductions in greenhouse gas emissions show

It will be DECADES before reductions in greenhouse gas emissions of carbon dioxide and other pollutants can be detected, scientists warn

  • Researchers calculated the time it would take for emission changes to be shown
  • This included looking at the impact on global surface temperatures over time 
  • They found previous emission reduction efforts won’t be detectable until 2035
  • This means any programs to reduce emissions need to be long-term focused 

It is going to take decades before any efforts to reduce the amount of greenhouse gases such as carbon dioxide can be detected, scientists warn.

Experts from the CICERO Center for International Climate Research analysed how global warming will evolve under different assumptions on emission reductions.  

The impact of significant reductions in human emissions – needed to slow global warming – will take decades to be visible in global surface temperatures.

This is partly due to the fact that the Earth’s climate responds slowly to emission changes and the fact the annual mean temperature is naturally variable.

It could be 2035 before we see any impact from emission reduction efforts made over the past few decades but that doesn’t mean they aren’t making a difference. 

The authors say that their findings suggest that climate change mitigation demands long-term commitment, as short-term effects cannot be expected. 

Experts from the CICERO Center for International Climate Research analysed how global warming will evolve under different assumptions on emission reductions

Over the past 50 years, the Earth’s surface temperature has increased by 0.36F (0.2C) every decade, mainly due to human induced greenhouse gas emissions. 

‘Human-induced climate change can be compared with a tank ship at high speed and in big waves,’ said study author Bjørn Samset.

‘If you want the ship to slow down, you will put the engine in reverse, but it will take some time before you start noticing that the ship is moving more slowly. 

‘It will also rock back and forth because of the waves,’ Samset explained.

There are also large variations from one year to the next which are on a similar scale, according to the Centre for International Climate and Environmental Research team. 

They said the first step in achieving the Paris Agreement of limiting global warming to no more than 3.6F (2C) will be to slow the warming process.

‘But although the necessary emissions reductions are effective from day one, it will take some time before we can measure this effect with certainty,’ he says.

In addition to being impacted by greenhouse gas emissions, the Earth’s climate is also characterised by a lot of natural variability.  

Dr Amanda Maycock, Associate Professor in Climate Dynamics, University of Leeds, said making ‘rapid and ambitious reductions in multiple emission sources gives us a very good chance of avoiding extreme warming rates in the next two decades. 

She said natural fluctuations in climate can obscure the effects of those changes even on a ten year time frame, as seen by the study, but the work is essential.

One of the main goals of this study was to find out how we can expect the global surface temperature to develop – based on human and natural factors. 

‘Just like it took some time to establish that global warming is happening, we will need to have some patience before we can determine that the actions taken to limit global warming are having the desired effect,’ he explains.

Samset and his colleagues estimate that even for the most optimistic scenarios, there is a risk that it will not be possible to establish that the emissions cuts have had an impact on global warming before 2035. 

However, that does not mean that the emissions reductions are not having the desired effect, according to Samset.

‘The effects of climate cuts can be compared with those resulting from social distancing during an epidemic,’ the study author explained.

‘They work from day one, but because of the incubation time, it will take some time before you can see the effect on the infection rates,’ he says.

All reductions in warming emissions will lead to less heat being absorbed – but will take time before it can be measures effectively. 

Tim Palmer, Royal Society Research Professor, University of Oxford, and not involved in this study said these are new results, not to be compared with previous studies.

‘It bothers me a little that some non-experts may interpret the word “delayed” in the title of this paper as meaning “compared with what we previously thought”. 

Authors said the first step in achieving the Paris Agreement of limiting global warming to no more than 3.6F (2C) will be to slow the warming process

‘Fundamentally these are not new results: just as we knew that it takes some time for the climate-change signal to emerge from the noise on the way up, we knew that it will take some time for a reduced climate-change signal to emerge from the noise on the way down,’ he explained.

There are other measures for detection such as estimating emission reductions and if there is a slower increase in the amount of greenhouse gas they will show it.

‘But for temperature, which is what we really care about – and which, among other things, has an impact on the increased frequency and severity of extreme weather – it will take decades before we will be able to measure the effect,’ he says. 

The study has also analysed the effect of cutting one single type of emissions, such as methane, soot, or carbon dioxide (CO2). 

‘Different emissions affect the climate in various ways, and some have a stronger and more rapid effect on global temperature,’ said co-author Jan Fuglestvedt. 

The team found that the human-induced emissions with the biggest impact on global warming are CO2 and methane. 

‘If these emissions are reduced very strongly, we will see the effect quickly. But if reductions follow more realistic pathways, it will take longer,’ says Fuglestvedt. 

The emissions cuts necessary to limit global warming in line with the goals of the Paris Agreement will require rapid, major changes in society, the team said.

This would include changes to both businesses and the energy sector.

Although this must happen quickly, we still need to have realistic expectations about how long it will take before we see a temperature effect of these changes, according to the CICERO researchers.

‘We performed this study partly to remind us all that things will take time.’  

The findings have been published in the journal Nature Communications.

Revealed: MailOnline dissects the impact greenhouse gases have on the planet – and what is being done to stop air pollution


Carbon dioxide

Carbon dioxide (CO2) is one of the biggest contributors to global warming. After the gas is released into the atmosphere it stays there, making it difficult for heat to escape – and warming up the planet in the process. 

It is primarily released from burning fossil fuels such as coal, oil and gas, as well as cement production. 

The average monthly concentration of CO2 in the Earth’s atmosphere, as of April 2019, is 413 parts per million (ppm). Before the Industrial Revolution, the concentration was just 280 ppm. 

CO2 concentration has fluctuated over the last 800,000 years between 180 to 280ppm, but has been vastly accelerated by pollution caused by humans. 

Nitrogen dioxide 

The gas nitrogen dioxide (NO2) comes from burning fossil fuels, car exhaust emissions and the use of nitrogen-based fertilisers used in agriculture.

Although there is far less NO2 in the atmosphere than CO2, it is between 200 and 300 times more effective at trapping heat.

Sulfur dioxide 

Sulfur dioxide (SO2) also primarily comes from fossil fuel burning, but can also be released from car exhausts.

SO2 can react with water, oxygen and other chemicals in the atmosphere to cause acid rain. 

Carbon monoxide 

Carbon monoxide (CO) is an indirect greenhouse gas as it reacts with hydroxyl radicals, removing them. Hydroxyl radicals reduce the lifetime of carbon dioxide and other greenhouse gases. 


What is particulate matter?

Particulate matter refers to tiny parts of solids or liquid materials in the air. 

Some are visible, such as dust, whereas others cannot be seen by the naked eye. 

Materials such as metals, microplastics, soil and chemicals can be in particulate matter.

Particulate matter (or PM) is described in micrometres. The two main ones mentioned in reports and studies are PM10 (less than 10 micrometres) and PM2.5 (less than 2.5 micrometres).

Air pollution comes from burning fossil fuels, cars, cement making and agriculture 

Scientists measure the rate of particulates in the air by cubic metre.

Particulate matter is sent into the air by a number of processes including burning fossil fuels, driving cars and steel making.

Why are particulates dangerous?

Particulates are dangerous because those less than 10 micrometres in diameter can get deep into your lungs, or even pass into your bloodstream. Particulates are found in higher concentrations in urban areas, particularly along main roads. 

Health impact

What sort of health problems can pollution cause?

According to the World Health Organization, a third of deaths from stroke, lung cancer and heart disease can be linked to air pollution. 

Some of the effects of air pollution on the body are not understood, but pollution may increase inflammation which narrows the arteries leading to heart attacks or strokes. 

As well as this, almost one in 10 lung cancer cases in the UK are caused by air pollution. 

Particulates find their way into the lungs and get lodged there, causing inflammation and damage. As well as this, some chemicals in particulates that make their way into the body can cause cancer. 

Deaths from pollution 

Around seven million people die prematurely because of air pollution every year. Pollution can cause a number of issues including asthma attacks, strokes, various cancers and cardiovascular problems. 


Asthma triggers

Air pollution can cause problems for asthma sufferers for a number of reasons. Pollutants in traffic fumes can irritate the airways, and particulates can get into your lungs and throat and make these areas inflamed. 

Problems in pregnancy 

Women exposed to air pollution before getting pregnant are nearly 20 per cent more likely to have babies with birth defects, research suggested in January 2018.

Living within 3.1 miles (5km) of a highly-polluted area one month before conceiving makes women more likely to give birth to babies with defects such as cleft palates or lips, a study by University of Cincinnati found.

For every 0.01mg/m3 increase in fine air particles, birth defects rise by 19 per cent, the research adds. 

Previous research suggests this causes birth defects as a result of women suffering inflammation and ‘internal stress’. 

What is being done to tackle air pollution? 

Paris agreement on climate change

The Paris Agreement, which was first signed in 2015, is an international agreement to control and limit climate change. 

It hopes to hold the increase in the global average temperature to below 2°C (3.6ºF) ‘and to pursue efforts to limit the temperature increase to 1.5°C (2.7°F)’.

Carbon neutral by 2050 

The UK government has announced plans to make the country carbon neutral by 2050. 

They plan to do this by planting more trees and by installing ‘carbon capture’ technology at the source of the pollution.

Some critics are worried that this first option will be used by the government to export its carbon offsetting to other countries.

International carbon credits let nations continue emitting carbon while paying for trees to be planted elsewhere, balancing out their emissions.

No new petrol or diesel vehicles by 2040

In 2017, the UK government announced the sale of new petrol and diesel cars would be banned by 2040. 

From around 2020, town halls will be allowed to levy extra charges on diesel drivers using the UK’s 81 most polluted routes if air quality fails to improve.

However,  MPs on the climate change committee have urged the government to bring the ban forward to 2030, as by then they will have an equivalent range and price.

The Paris Agreement, which was first signed in 2015, is an international agreement to control and limit climate change. Pictured: air pollution over Paris in 2019.

Norway’s electric car subsidies

The speedy electrification of Norway’s automotive fleet is attributed mainly to generous state subsidies. Electric cars are almost entirely exempt from the heavy taxes imposed on petrol and diesel cars, which makes them competitively priced.

A VW Golf with a standard combustion engine costs nearly 334,000 kroner (34,500 euros, $38,600), while its electric cousin the e-Golf costs 326,000 kroner thanks to a lower tax quotient. 

Criticisms of inaction on climate change

The Committee on Climate Change (CCC) has said there is a ‘shocking’ lack of Government preparation for the risks to the country from climate change. 

The committee assessed 33 areas where the risks of climate change had to be addressed – from flood resilience of properties to impacts on farmland and supply chains – and found no real progress in any of them.

The UK is not prepared for 2°C of warming, the level at which countries have pledged to curb temperature rises, let alone a 4°C rise, which is possible if greenhouse gases are not cut globally, the committee said.

It added that cities need more green spaces to stop the urban ‘heat island’ effect, and to prevent floods by soaking up heavy rainfall. 

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