Climate science

Hydrofluorocarbon emissions up 54% with air conditioning on the rise

  • 27 Apr 2015, 20:00
  • Robert McSweeney

As spring temperatures in the UK inched above 20C in recent weeks, air conditioners in offices across the country will have rumbled into life after a silent winter.

But while these machines cool our buildings and cars, they could be having an increasing warming effect on the planet, a new study says.

Air conditioners and fridges contain potent greenhouse gases known as hydrofluorocarbons (HFCs). The new research shows global emissions of HFCs have risen by more than half between 2007 and 2012.

And as temperatures and incomes rise during this century, air conditioning use is set to grow rapidly in warm countries around the world, a second study finds.

Potent greenhouse gases

In 1987, countries around the world signed the Montreal Protocol, an agreement to phase out use of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs).

Scientists had found the gases were depleting the ozone layer, the atmospheric shield that filters the Sun's harmful ultraviolet radiation from reaching the Earth's surface.

CFCs and HCFCs were used as refrigerants in air conditioning units and fridges, propellants in aerosol sprays, and fire suppressants in extinguishers.

Scientists invented HFCs to take their place. HFCs don't damage the ozone layer, but as with their predecessors, they are potent greenhouse gases - as much as several thousand times stronger at absorbing heat than carbon dioxide.

Now a new study, published in Proceedings of the National Academy of Sciences, finds their emissions have risen rapidly in just five years.

Dramatic rise

Researchers estimated the abundance of the five most common HFCs from two global datasets: the Advanced Global Atmospheric Gases Experiment (AGAGE) and Japan's National Institute Environmental Studies (NIES ).

The data showed a dramatic rise in HFC emissions from 303 to 463 million tonnes of carbon dioxide equivalent between 2007 and 2012. This equates to an increase of 33 million tonnes per year, similar to the annual fossil fuel carbon emissions of New Zealand, the researchers say.

You can see this increase as the blue line in the graph below. The researchers also divided the results between developed countries (Annex I, green line) and developing countries (Non-Annex I, red line).

Lunt Et Al 2015 Fig2

Combined emissions of five HFCs from 2007 to 2012 for the world (blue line), developed countries only (green) and developing countries only (red line). Dotted and dashed black lines show emissions reported to the UNFCCC (for developed countries only). Grey, orange and purple lines show estimates from other studies. Source: Lunt et al. (2015)


World's plants and soils to switch from carbon sink to source by 2100, study shows

  • 24 Apr 2015, 15:40
  • Robert McSweeney

Every year, trees and plants across the world absorb a vast amount of carbon dioxide from the atmosphere.

But a new study suggests this massive carbon sink could instead become a source of carbon dioxide by the end of the century.

This means we might not be able to rely on plants soaking up our emissions for much longer, the lead author tells Carbon Brief.

Extra carbon dioxide

Through photosynthesis, plants convert carbon dioxide, water and sunlight into the fuel they need to grow, locking up carbon in their branches, stems and leaves in the process.

Research suggests that as human-caused carbon dioxide emissions accumulate in the atmosphere, plants will grow more quickly because the rate of photosynthesis speeds up. This is called 'carbon dioxide fertilisation'.

This argument is sometimes used in parts of the media to suggest that additional carbon dioxide is beneficial for the Earth as extra food for plants.

But research published this week in Nature Geoscience suggests that plants won't have enough nutrients to make full use of the extra carbon dioxide in the atmosphere.  So any benefits will be limited, say the authors.

Nutrient needs

Plants need the right mix of nutrients to grow. Two of the most important nutrients are nitrogen and phosphorus. But there isn't an endless supply in soils for plants to use, lead author Dr Will Wieder, from the National Centre for Atmospheric Research in Colorado, tells Carbon Brief:

"Many ecosystems appear to be co-limited, meaning that both nitrogen and phosphorus are important for plant growth. There are places where one element or the other may be slightly more limiting, but at the end of the day plants need both to build roots, leaves and wood. This is why many fertilizers used in gardens and farms come with both nitrogen and phosphorus."

While nitrogen is abundant in the air we breathe, most plants can only take it up from the soil. Nitrogen gets into the soil by being 'fixed' from the air by microbes and certain plants, such as soy, Wieder says. Phosphorus primarily originates from rocks, and reaches the soil when they are worn down by the weather.

Nutrients can come from a little further afield as well, Weider adds:

"Both nitrogen and phosphorus can be moved around and transported through the atmosphere as dust or air pollution. The subsequent deposition of nitrogen and phosphorus also can contribute new nutrients to an ecosystem."


What do volcanic eruptions mean for the climate?

  • 23 Apr 2015, 15:35
  • Robert McSweeney & Roz Pidcock

Having lain dormant for over 40 years, the Calbuco volcano last night erupted twice within the space of a few hours. The blast sent a huge cloud of ash over southern Chile.

Carbon Brief has asked a number of experts what volcano eruptions mean for the climate, and whether or not we can expect this latest event to have global consequences.

Cooling effect

Volcanic eruptions can affect climate in two main ways.

First, they release the greenhouse gas carbon dioxide, contributing to warming of the atmosphere. But the effect is very small. Emissions from volcanoes since 1750 are thought to be at least 100 times smaller than those from fossil fuel burning.

Second, sulphur dioxide contained in the ash cloud can produce a cooling effect, explains Prof Jim McQuaid, professor of atmospheric composition at the University of Leeds:

"Sulphur dioxide is quickly converted into sulphate aerosol which then alongside the fine volcanic ash forms a partial barrier to incoming solar radiation"

You can see this in the NASA video below that maps movements of particles in the Earth's atmosphere. At around 2 minutes in you can see the impact of the volcanic eruption in Madagascar, just off the eastern coast of Africa.