Analysis

Chance of a very cold UK winter falls to less than 1% by 2100, new study suggests

  • 06 Jul 2015, 16:00
  • Robert McSweeney

The odds of the UK having a winter as cold as the one in 2009-10 will drop to less than 1% by the end of the century as global temperature rise, researchers from the UK Met Office say.

The new research combines long-term projections of climate change with the yearly ups and downs of the UK's notoriously changeable weather. 

The results suggest that very cold winters and wet summers will become less and less likely, but the research says we should still expect them from time to time.

Cold snap

Climate projections tend to focus on how the typical weather of each season will change in the future. Yet British weather is often anything but typical.

Projections of climate change tell us that UK winters are likely to  get milder. Yet the winter of 2009-10 was the coldest in England and Wales for over 30 years, with average temperatures around  2C below the 1971-2000 average

This "apparent contradiction" led  some parts of the media to create confusion by claiming that our climate isn't warming at all, say the authors of a new study in Nature Climate Change.

But there isn't a contradiction at all, they say. And so they set out to show how a cold winter or a wet summer could still happen in a much warmer world - even if they are much less likely. 

Weather and climate

The researchers used the 'UK Climate Projections 2009' (UKCP09 ) - a set of projections of our future climate averaged into 30-year chunks, from 2010-2039, all the way to 2070-2099. They then combined them with model projections that are averaged over just a single year, and thus include more of the year-to-year variability in our weather. 

The resulting graphs, shown below, illustrate how different aspects of our weather are expected to change under a moderate emissions scenario. The black lines show observed changes and the red, blue and yellow lines show three (of many) different runs of their climate model. 

Annual Global Vs England Wales Temp

Observed (black lines) and projected (coloured lines) changes temperature/rainfall for individual seasons under the  A1B emissions scenario for England and Wales. Data show difference from the 1961-90 average. Source: Sexton and Harris (2015)

The results show how even with a clear climate change trend, we are still likely to be on the receiving end of some highs and lows of British weather, the researchers say.

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The most influential climate change papers of all time

  • 06 Jul 2015, 12:00
  • Roz Pidcock
Front covers of the most influential climate papers

Climate papers | Carbon Brief

Which of the many thousands of papers on climate change published each year in scientific journals are the most successful? Which ones have done the most to advance scientists' understanding, alter the course of climate change research, or inspire future generations?

On Wednesday, Carbon Brief will reveal the results of our analysis into which scientific papers on the topic of climate change are the most "cited". That means, how many times other scientists have mentioned them in their own published research. It's a pretty good measure of how much impact a paper has had in the science world.

But there are other ways to measure influence. Before we reveal the figures on the most-cited research, Carbon Brief has asked climate experts what they think are the most influential papers.

We asked all the coordinating lead authors, lead authors and review editors on the last Intergovernmental Panel on Climate Change (IPCC) report to nominate three papers from any time in history. This is the exact question we posed:

"What do you consider to be the three most influential papers in the field of climate change?"

As you might expect from a broad mix of physical scientists, economists, social scientists and policy experts, the nominations spanned a range of topics and historical periods, capturing some of the great climate pioneers and the very latest climate economics research.

Here's a link to our  summary of who said what. But one paper clearly takes the top spot.

Winner: Manabe & Wetherald (  1967)

With eight nominations, a seminal paper by Syukuro Manabe and Richard. T. Wetherald published in the Journal of the Atmospheric Sciences in 1967 tops the Carbon Brief poll as the IPCC scientists' top choice for the most influential climate change paper of all time.

Entitled, "Thermal Equilibrium of the Atmosphere with a Given Distribution of Relative Humidity", the work was the first to represent the fundamental elements of the Earth's climate in a computer model, and to explore what doubling carbon dioxide (CO2) would do to global temperature.

Fig1  Manabe & Wetherald (1967), Journal of the Atmospheric Sciences

The Manabe & Wetherald paper is considered by many as a pioneering effort in the field of climate modelling, one that effectively opened the door to projecting future climate change. And the value of climate sensitivity is something climate scientists are  still grappling with today.

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Solar minimum could bring cold winters to Europe and US, but would not hold off climate change

  • 23 Jun 2015, 16:00
  • Robert McSweeney
Low winter sun over a common

Winter sun | Flickr

Over the past few decades, our Sun has been relatively active, giving off high levels of the solar radiation that warms the Earth. However, in recent years this peak activity has tailed off, prompting scientists to wonder if the Sun is heading into a period of lower output.

A new study says even if the Sun's activity did drop off for a while, it wouldn't have much impact on rising global temperatures. But it could mean a higher chance of a chilly winter in Europe and the US, the researchers say.

Solar output

The Sun's activity rises and falls on an approximately 11-year cycle, but it can experience longer variations from one century to another. Over the past 10,000 years, the Sun has hit around 30 periods of very high or very low activity - called 'grand maxima' and 'grand minima'.

One of these occurred between 1645 and 1715, when the Sun went through a prolonged spell of low solar activity, known as the Maunder Minimum. This didn't have much of an effect on global climate, but it was linked to a number of  very cold winters in Europe.

In 2010, scientists  predicted an 8% chance that we could return to Maunder Minimum conditions within the next 40 years.

But since that study was published, solar activity has declined further, and this likelihood has increased to 15 or 20%, says new research published today in open-access journal Nature Communications.

In fact, the Sun's output has declined faster than any time in our 9,300-year record, say the researchers. And so they set out to analyse what this could mean for global and regional climate.

Small decrease

The researchers used a climate model to run two scenarios where solar activity declines to a grand minimum. They then compared the results with a control scenario where the Sun continues on its regular cycle.

For all model runs they used the RCP8.5 scenario to account for future climate change - this is the scenario with the highest greenhouse gas emissions of those used by the Intergovernmental Panel on Climate Change ( IPCC). Global emissions are currently tracking just above this scenario.

You can see the modelling results in the maps below. Overall, a grand solar minimum could see global average temperature rise trimmed by around 0.12C for the second half of this century, the researchers say. Larger changes (shown as dark greens and blues) are seen in some parts of the northern hemisphere.Ineson Et Al (2015) Fig2Projected difference in annual average surface temperature for 2050-99 between RCP8.5 emissions scenario and a) Solar scenario 1 and b) Solar scenario 2. Areas of blue and green show regions projected to be cooler because of the solar minimum. Source: Ineson, S. et al. (2015)

 

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Tackling climate change will reap benefits for human health

  • 23 Jun 2015, 00:01
  • Roz Pidcock

Curbing climate change could be the biggest global health opportunity of the 21st century. But if we choose not to act, we could reverse all the progress made by economic development in the last 50 years towards improving global public health.

These are the conclusions of a new report by the Lancet Commission out today.

Curbing air pollution, phasing out coal, access to clean energy worldwide and promoting healthier lifestyles would have "immediate gains" for human health, says the report. 

The authors also call for a global price on carbon and a scaling-up of adaptation financing.

The Lancet Commission is a body set up to map out the impacts of climate change on health, and make recommendations to improve health standards worldwide.

Today's report is a collaboration between European and Chinese academics across the physical, health, political and social sciences, economics, energy policy and engineering.

Impacts are here and now

The risks posed by climate change are already unacceptably high, today's report begins:

"After only 0.85C warming, many anticipated threats have already become real-world impacts."

And if we continue to track the highest emissions scenarios - taking us to  4C or 5C by the end of the century - the risk of potentially catastrophic impacts rises even higher, the report adds.

Screenshot 2015-06-22 17.21.32

Changing exposure in over 65s to heatwaves by 2090 for RCP8.5 (left). Growth in annual heatwave exposure for over 65s with and without accounting for a growing and ageing population (right). Source: Lancet Commission report on health and climate change (2015)

The impacts of climate change on human health are all-pervading. Small risks can interact to produce larger-than-expected chances of catastrophic outcomes, the report notes.

As well as the  direct effects of rising temperatures on heat stress, floods, drought and other extreme weather, climate change increases air pollution, alters the spread of disease and raises the risk of food insecurity, malnutrition, migration and conflict.

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Climate change attribution studies are asking the wrong questions, study says

  • 22 Jun 2015, 16:30
  • Robert McSweeney
Devastation after cyclone Pam

Cyclone Pam | Wikimedia

Scientists are calling for a rethink in the way we seek to understand how climate change affects extreme weather.

The latest in so-called attribution studies is to study each  individual event by itself, looking for how climate change may have made it stronger or more likely.

But a new paper says the methods used in many of these studies underestimate the influence of climate change, and suggests a new approach to identify the "true likelihood of human influence".

Single-event attribution

One of the first studies to attribute a single extreme weather event to climate change was published just over a decade ago. Researchers  showed that climate change had doubled the chances of the record heatwave Europe experienced in 2003.

In the years that followed, many more studies have aimed to provide answers on how climate change is affecting our most brutal weather.

But while scientists have been able to attribute events caused by temperature extremes, linking other extreme events like storms and heavy rainfall events has proved more difficult, says a new paper in Nature Climate Change.

Canicule _Europe _2003Difference in temperature for 20 July to 20 August 2003 compared to long-term average. Source: Reto Stockli and Robert Simmon (NASA).

In our chaotic weather system, the complex dynamics of the atmosphere mean the size and path of a storm or heavy rainfall event has a large element of chance, the authors say. This can make it tricky to identify where climate change fits in.

But rather than analysing the wind patterns that bring a storm to an area, scientists should be looking at how the impact of that storm has been boosted by temperature changes -  known as thermodynamic effects.

Temperature increases mean more moisture evaporates into the atmosphere and more ice melts into our warming oceans, raising their levels. These are changes that scientists can be confident of, the authors say, and so should be the basis for attribution studies - rather than looking at changes to circulation patterns in the atmosphere.

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The Atlantic 'conveyor belt' and climate: 10 years of the RAPID project

  • 19 Jun 2015, 18:40
  • Roz Pidcock and Robert McSweeney

A global project that's been instrumental in shaping scientists' understanding of how the oceans affect our climate celebrated its tenth birthday recently.

A new paper published in  Science looks back at 10 years of the  RAPID project, which has been keeping tabs on how heat moves around in the Atlantic Ocean since 2004.

Over its short lifetime, the project has thrown up a few surprises. Parts of the Atlantic circulation seem to have slowed down, though whether that's down to human activity remains to be seen.

Carbon Brief talks to one of RAPID's founding scientists, Prof Harry Bryden from the National Oceanography Centre in Southampton, about the project's past and future.

Global heat transport

Above about 1,000 metres in the North Atlantic, warm water flows northwards from the equator towards the poles, releasing heat as it goes. The water cools and sinks at high latitudes, returning southwards towards the equator at much deeper depths.

This is known as the Atlantic Meridional Overturning Circulation (AMOC) and forms part of a global ocean conveyor belt that transports heat all around the world.

                 Screenshot 2015-06-19 18.22.21

The Atlantic Meridional Overturning Circulation (AMOC). Warm water flows north in the upper ocean (red arrows) then sinks and returns south as deep cold water (blue arrows) Source: Srokosz & Bryden (  2015) Supplementary material

The Gulf Stream - another component of the AMOC - is driven by the wind. Heat released to the atmosphere as the warm Gulf Stream moves northward gives northwest Europe its mild climate.

All components of the AMOC together transport about 18 million cubic metres of water per second - equivalent to a hundred times the flow from the Amazon river. The heat carried with it means North Atlantic sea surface temperature is about  5C warmer than in the North Pacific at similar latitudes.

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Oxygen is an overlooked factor in past climate, study suggests

  • 11 Jun 2015, 19:00
  • Robert McSweeney
A view of the Earth and stars from space

Earth from space | Shutterstock

It's well established how carbon dioxide, methane and water vapour affect our climate. But a new study suggests another gas may have played a role in Earth's long climate history - oxygen.

Natural variations in atmospheric oxygen levels could be a missing factor in piecing together Earth's past climate, the researchers say. The findings help explain why climate models tend to simulate temperatures 100m years ago that are lower than scientific evidence suggests.

Oxygen levels

Today, oxygen makes up around 21% of the air we breathe. But that hasn't always been the case. Over the last 500m years, known as the Phanerozoic eon, oxygen levels have been as low as 10% and as high as 35%.

This period has seen the evolution of life as we know it, and scientists know that changes in atmospheric oxygen has been intertwined with how life on Earth has thrived .

Now new research, published today in the journal Science, suggests that oxygen may have had a role in how our climate evolved as well.

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Climate change could cut growing days of plants and crops by 11%

  • 11 Jun 2015, 10:45
  • Robert McSweeney

Sunrise over meadow | Shutterstock

The number of days each year when conditions are suitable for plants to grow could fall as the climate warms, according to new research.

Researchers in Hawaii found rising temperatures and falling soil moisture could curtail growth of plants and crops across much of the tropics. And if emissions remain unchecked, gains in plant growth at higher latitudes won't make up for these losses.

But other scientists, not involved in the study, tell Carbon Brief the new research may have overestimated the negative impacts of climate change.

Plant growth

Climate change is likely to have both positive and negative impacts on plant growth.

A warmer, more carbon-rich atmosphere could provide better conditions for growth. On the other hand, rising temperatures could make conditions too hot for plant growth. How much water and nutrients plants and crops have access to will also affect how much they can grow.

Scientists have conducted numerous studies into how these factors are likely to play out for different plants and different regions of the world.

The new study, published in open-access journal PLoS Biology, takes a different approach. Rather than estimating how much plants might grow, the researchers focus on how many days each year we'll see conditions favourable for plant growth in the future.

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Climate change risks biggest change to marine species in three million years

  • 01 Jun 2015, 16:00
  • Dr Grégory Beaugrand & Dr Richard Kirby
Photo of a tropical fish on a coral reef

Tropical reef | Shutterstock

A guest post by Dr Grégory Beaugrand, researcher at the University of Lille Laboratory of Oceanography and Geoscience, and Dr Richard Kirby, research fellow at the Marine Biological Association of the UK.

Humans rely heavily on the world's oceans. About 70% of the world population lives within 60km of the shoreline, and we catch around 80 million tonnes of fish every year. In our new study, we investigate how warming oceans could affect the spread of marine species.

And the results suggest warming over 2C would have a bigger impact on marine biodiversity than we've seen in the last three million years.

Marine biodiversity

We know very little about the many and varied species swimming around in our oceans. Scientists estimate there are around two million different species globally, but so far we have only identified around a tenth of them. This lack of knowledge makes it difficult to predict how climate change could affect marine ecosystems.

But it remains an important challenge.

Until now, attempts to understand the implications of climate change on marine biodiversity have either projected results based on a few key species, or used statistical models to predict the distribution of a species based on different environmental factors.

Both methods are limited by our knowledge of how species are distributed across our oceans. In our study, published today in Nature Climate Change, we take a different approach - using ocean temperatures.

Theoretical species

We use a novel approach based upon the theory that the way biodiversity is distributed in the ocean is based on the temperatures that different species can tolerate and thrive in.

In our ecological model, we created tens of thousands theoretical species. We gave each species a unique response to ocean temperature and allowed them to colonise the world's oceans, wherever they found the temperatures were suitable for them.

To make sure our pseudo-global aquarium was realistic, we checked it against observed data for real species, including types of plankton, crustaceans and fish.

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Warming oceans could mean typhoons are 14% stronger by 2100, study says

  • 29 May 2015, 19:00
  • Robert McSweeney
International Space Station Image of Haiyan

Typhoon Haiyan | Flickr

On 7 November 2013, one of the strongest typhoons in human history hit the Philippines. With gusts up to 171 miles per hour (mph), Typhoon Haiyan tore through the many thousands of islands, killing over 6,200 people and affecting 14 million more.

Every year, these giant storms cause damage and destruction across southeast Asia. Now, a new study suggests that even under a moderate temperature rise, warming oceans could fuel more intense typhoons in the future.

Peak wind speeds

Large tropical storms, sometimes referred to collectively as tropical cyclones, have different names in different parts of the world. In countries around the North Atlantic such as the UK, for example, we call them hurricanes. In the northwest Pacific Ocean, they are known as typhoons.

Typhoon strength is measured by wind speed. Anything over 74 miles per hour (mph) is classified as category one, while only the strongest events with wind speeds over 156 mph reach category five. In the new study, published in Science Advances, researchers assessed how climate change could affect the maximum wind speed of typhoons.

Using typhoon wind speed records for the past 60 years, the researchers looked at how the strength of typhoons has changed. Today, typhoon wind speeds are around 10% stronger than they were in the 1970s.

The destruction caused by a typhoon doesn't just rise in line with wind speed. A 10% rise translates to a 33% increase in destructiveness, the researchers say.

We're also seeing an increasing number of typhoons reaching the highest intensity categories, the study says. 

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