Climate science

Q & A: What’s El Niño - and why does it matter that scientists say one is on the way?

  • 24 Apr 2014, 12:50
  • Roz Pidcock

Forecasters worldwide are issuing alerts. Later this year, we're likely to be in the midst of an El Niño - a phenomenon driving severe weather worldwide. So when can we expect it to kick in, and what will the consequences be for global temperature? Find this and more in our quick Q & A.

What is an El Niño?

Every five years or so, a change in the winds causes a shift to warmer than normal ocean temperatures in the  equatorial Pacific Ocean - known as El Niño, or cooler than normal - known as La Niña, moving briefly back to normal in between.

Both phases together are known as the El Niño Southern Oscillation (ENSO), and are responsible for most of the fluctuations in global weather we see from one year to the next.

ENSO

Sea surface temperature during El Niño (left) and La Niña (right). Red and blue show warmer and cooler temperatures than the long term average. [Credit: Steve Albers, NOAA]

more

IPCC review of farming and forests leaves key questions about effect on climate change "unresolved"

  • 17 Apr 2014, 12:15
  • Robin Webster

The rate at which we're chopping down the world's forests is declining - and in future, crops and newly planted forests could help prevent more climate change, according to the UN.

But uncertainties surrounding how we measure emissions, and what changing temperatures will mean for the world's forests, mean it's hard to be sure this is a good news story.

Emissions from farming, deforestation and other land use are going down, and are expected to continue doing so in the future. By the end of the century, humanity could use the land as a carbon sink, rather than a source of emissions, according to the Panel on Climate Change (IPCC)'s latest  report

It sounds like one piece of good news among  gloomy predictions from the IPCC. But human land use is only one part of a complex picture. 

Climate change could lead to forests  drying out, releasing more carbon dioxide in the atmosphere. And using trees, crops and plants as a source of energy instead of fossil fuels could also lead to more forest destruction.  

Declining emissions

Agriculture, forestry and other land use account for about a quarter (24 per cent) of man-made greenhouse gas emissions. Most of these emissions come from deforestation, changes to the soil and livestock farming.

more

Degrees of change: the IPCC’s projections for future temperature rise

  • 15 Apr 2014, 12:00
  • Robin Webster

Many governments are trying to reduce greenhouse gas emissions. But unless policymakers raise their ambition significantly, temperatures are likely to rise beyond safe levels. We examine the pathways that could take us towards a two degrees temperature rise by the end of the century - or considerably higher. 

On Sunday, the Intergovernmental Panel on Climate Change (IPCC) released the last in a series of three reports, which together assess the physical evidence that climate change is happening, the  expected impacts over the course of this century and what would need to happen to curb the rise in greenhouse gases.

Embedded in the reports are the scientists' predictions for how high temperatures are likely to rise this century - and what that's likely to mean for ecosystems and societies around the world. 

Comparing scenarios 

The IPCC bases its projections for future temperature rise on two different techniques. 

First, the IPCC has created its own storylines, or scenarios, describing how high temperatures are likely to rise in the future and what that might mean. The scenarios vary according to different predictions for how societies develop and how much effort we make to reduce greenhouse gas emissions over the course of this century.

more