UN climate report: Why this is no longer “business as usual”

Image copyright TSB New research in the US State of California projected that temperatures could rise between 1.4C and 4.5C. Image caption How will your local council prepare for a 1.4C rise in temperatures?

Soaring temperatures due to rising carbon dioxide emissions could trigger rapid changes in the weather, the UN’s scientific body has warned.

A landmark report published by the Intergovernmental Panel on Climate Change (IPCC) could still boost the likelihood of tipping points in global warming.

It projects that the Earth will warm by between 1.8C and 4.5C.

If this were to occur, the likelihood of a damaging impact would increase.

This is of concern because currently, the IPCC’s review of climate science uses far too conservative a scenario, it says.

The language of the report was particularly tough, warning: “A high confidence exists that most of the observed increase in global average temperatures over the past 50 years is, in part, a result of human influence.”

For the first time, the IPCC used a reduced version of the mathematical model that it uses to test models of climate and attempts to explain the warming trend. This had been expected to bolster the scientific case.

Instead, the report seems to add to fears that global warming is already accelerating much faster than previously predicted.

For example, the report’s assessment of recent climate models suggests climate change in past decades is mostly a result of the weakening of Antarctic and Greenland ice sheets, caused by global warming. The report suggests that ice sheets could collectively lose over three trillion tonnes of mass between 2012 and 2030.

It also predicts that this could add 20C of warming between 1998 and 2020.

Image copyright Tibor Kozmenai Image caption Recent research from the University of Melbourne found that increasing temperatures could lead to heat waves lasting months

The IPCC’s warming curve is thought to have bottomed out in the mid-1990s and a steady rise has continued, eventually peaking in the 2000s. However, it is unclear whether the change in temperature is a trend or a temporary bubble effect.

A greater emphasis on the question of sea-level rise in the IPCC’s update may further strengthen predictions.

Extreme weather extremes, such as heatwaves, droughts and floods, seem to occur with “high confidence” in response to average warming. The frequency of these extreme events is projected to increase with average warming, with “high confidence” for heatwaves and “moderate confidence” for “water-stressed regions”.

The report concludes that the role of human behaviour in contributing to global warming is now “clear and increasing”.

Climate change is causing an increase in the number of extreme events such as the strong El Niño events in recent years, and the report includes research suggesting this alone could increase annual rainfall by 50%.

How will local councils prepare for a 1.4C rise in temperatures? Have your say

Images copyright Nasa Image caption Melting glaciers will damage the world’s water supplies.

The report says climate change is now “unequivocal”, with most parts of the globe warming more rapidly than in the past.

Despite this, the world has made no progress towards the ambitious greenhouse gas reduction targets set by the 2015 Paris climate change deal.

On average, warming continues to increase at the fastest rate seen in human history, surpassing the level that scientists believe was the product of natural climate variability and did not pose an immediate threat.

And our understanding of the response to climate change has changed dramatically in the past decade, more rapidly than any other such period in the past 2,000 years.

Experts say one of the main conclusions of the report is that this next 20 years, which is the panel’s longest period that has included a large amount of evidence, are critical to avoid dangerous levels of warming.

Many scientists and politicians have warned that global temperatures could hit the 3C mark if we continue on the path we are on, and will exceed the 5C threshold by 2100.

Image copyright Reuters Image caption Scientists may need to move beyond animal control to tackle the large numbers of heat waves

Dr Dermot Murtagh, a professor of biogeography at the University of East Anglia, told the BBC that greenhouse gas emissions will stay close to current levels for the next few years, but these would increase with the growth of the world economy.

“The fact that emissions are flat now, that’s partly down to economic growth and partly down to improved energy efficiency,” he said.

“We will still see emissions creep up in the next couple of years and those emissions are

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