The joker who brought climate science out of the cold

Wally Broecker, when he registered for the Columbia University geology department in 1953. Credit: Department of Earth and Environmental Engineering Archives, Columbia University

Wally Broecker, when he registered for the Columbia University geology department in 1953. Credit: Department of Earth and Environmental Engineering Archives, Columbia University

In Los Angeles on September 1 1955, the day temperatures reached a new record of 43°C, Wally Broecker stood, sweating, giving the first scientific talk of his life. He could scarcely have guessed where the new method he was telling an audience of sleepy archaeologists about, called radiocarbon dating, would send him. But thanks in part to its messages from history he would help spawn the phrase ‘global warming’ and warn of its effects, which have today pushed temperatures even higher.

Wally grew up and started college on the outskirts of Chicago, Illinois, good at maths, but largely uninterested in science. But college-mate Paul Gast steered his career sciencewards by helping get him a summer job at the new Lamont Geological Observatory that Paul had recently started working at. On June 15, 1952 Wally and pregnant wife Grace drove 800 miles to the Palisades, New York mansion Columbia University had inherited, and set up the observatory in. There, in the basement, Wally worked in and soon practically ran Laurence Kulp’s radiocarbon lab. Rather than lose him at the end of the summer Laurence organised for Wally to transfer to Columbia and stay working at Lamont, where he has remained ever since.

Taking advantage of the slow decay of a rare, radioactive form of carbon – carbon-14 – radiocarbon dating was in its infancy. The balance between carbon-14 and the usual form, carbon-12, is quite steady in CO2 in the air, and also in living plants that take up the gas as they grow. But when plants die, the carbon-14 they contain slowly decays to nitrogen. Measuring the ratio between the two forms of carbon, scientists can tell when the plants had died. But in 1952, Laurence’s lab was getting inconsistent readings, with carbon-14 counts sometimes coming out too high, even after Wally had fixed a problem with the equipment. Then Wally realised the problem came from outside the lab. The extra counts were coming from nuclear tests that had recently started over Nevada.

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Projected warming set to exceed civilisation’s experience

Oregon State University's Shaun Marcott has built a climate record reaching back 11,300 years, showing that today's temperatures are warmer than at least 70% of that period. Credit: Shaun Marcott

Oregon State University’s Shaun Marcott has built a climate record reaching back 11,300 years, showing that today’s temperatures are warmer than at least 70% of that period. Credit: Shaun Marcott

The world is headed for average surface temperatures warmer than it has seen in at least 11,300 years. That’s one conclusion US researchers have reached after bringing together 73 studies of ancient climate from across the world into a single global record. Their work supports previous records for the past 2,000 years built mainly from tree ring data, explained Shaun Marcott from Oregon State University, and gives a much broader view.

“We can put today’s global temperature into context against the entire Holocene period,” Shaun told me. “That’s when human civilisation was born, developed and progressed to today.” Modern temperatures are higher than in around three-quarters of that period, which reaches back to the end of the last ice age. And their comparison against forecasts for 2100 made in models used by the Intergovernmental Panel on Climate Change (IPCC) is even starker. “If those scenarios come to fruition, we’ll be well outside anything human civilisation has seen,” Shaun warned. “We won’t have even have been close.”

Knowing climate’s history helps understand its present, and so researchers have puzzled out temperatures on the Earth’s surface from proxy, or indirect, records for the last 2,000 years. In particular, bringing together measurements from tree rings, ice and coral has showed a sharp recent temperature rise often referred to as the ‘hockey stick’. Meanwhile, studies scattered across the world had reached back across the 11,300 years since the beginning of the Holocene. But they can be influenced by regional effects, and no one had pieced them into a global view that would overcome that. Read the rest of this entry »

Temperature cuts swathe through Australian seaweed

A mixed seaweed canopy in Western Australia, including Scytothalia dorycarpa (far right), which was completely killed along 100km of the Australian coast by a heatwave in 2011. Credit: Dan Smale

A mixed seaweed canopy in Western Australia, including Scytothalia dorycarpa (far right), which was completely killed along 100km of the Australian coast by a heatwave in 2011. Credit: Dan Smale

A record-breaking heat wave in 2011 killed a seaweed species that many fish and other creatures call home along a 100 km stretch of the Western Australian coast. That underlines the threat from climate change, which is driving more regular ‘extreme events’ like heatwaves, according to Dan Smale of the University of Western Australia (UWA). “Extreme events can wipe out species at their range edge incredibly quickly, which may have wide ranging implications for whole communities of associated plants and animals,” he said.

Metre-plus tall strands of Scytothalia dorycarpa seaweed sway around cool water rocky reefs in southern Australia, forming a playground for other species. It is thought to have evolved in cool conditions, and therefore to be sensitive to warmth. For that reason, in 2006, Dan and his UWA colleague Thomas Wernberg started tracking it in two main locations, Jurien Bay and Hamelin Bay, and 27 other sites. “We suggested that by monitoring its abundance and distribution, we could detect ecologically-significant climate change impacts over periods of years to decades,” Dan said. “We did not realise, however, that the highest-magnitude seawater warming event on record was just around the corner, and we did not expect to see such sudden and extensive shifts in its distribution.”

That extreme was reached in 2011 during the cooler ‘La Niña’ phase of the El Niño Southern Oscillation climate cycle. By contrast to the current Australian heatwave, temperatures rose thanks to an especially strong La Niña increasing the flow of warm water from the tropics. In March 2011 Thomas and Dan measured sea surface temperatures up to 4°C higher than the average for 2006-2010. The heatwave temperatures stayed more than 2°C above the 2006-2010 level for around 10 weeks in both bays. Read the rest of this entry »

Teeming tropical seas face exodus to cooler water

Organisms like these marine sea slugs must adapt to new temperatures or move to new areas to stay in the same ones. Image courtesy of Hugh Brown, Scottish Association for Marine Science

Organisms like these marine sea slugs must adapt to new temperatures or move to new areas to stay in the same ones. Image courtesy of Hugh Brown, Scottish Association for Marine Science

Though oceans are warming more slowly than land on average, climate changes still put sea creatures under similar pressure to those on dry land. That’s what Michael Burrows from the Scottish Marine Institute in Oban and 18 other researchers from eight different countries found by analysing the world’s surface temperature over the past 50 years. They brought together rates and directions of temperate change into a measure called “velocity of climate change”, showing how quickly and far species would have to move to stay in a similar environment. “It so happens that there are an awful lot of species in some of the places where velocities are highest, especially in the tropical oceans,” Burrows told Simple Climate. “That may have damaging effects on the richness of species in those places, especially in the hottest places, where there can be no immigrants from even hotter places to replace those that leave.”

The team from the "Towards understanding marine biological impacts of climate change" project that produced this work. Michael Burrows is on the left hand side of the middle row. Credit: University of California, Santa Barbara

The team from the "Towards understanding marine biological impacts of climate change" project that produced this work. Michael Burrows is on the left hand side of the middle row. Credit: University of California, Santa Barbara

These findings are the outcome of a series of meetings the researchers held at the University of California, Santa Barbara to assess the evidence for ocean life responding to climate change. “It struck us right away that there were no expectations available for how far organisms should shift to track temperatures, or by how much earlier or later they should do things seasonally,” Burrows explained. “We thought we could analyse temperature data to make these predictions.” Once they decided to do the analysis, it was surprisingly easy, the ecologist said, as worldwide temperature data is already available for the 20th century and up to the present.

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More turtles could become fish supper with warming

University of Queensland's David Booth and Andrew Evans have tested the effect of temperature on the swimming ability of the endangered green turtle. Credit: Nick Holmes

University of Queensland's David Booth and Andrew Evans have tested the effect of temperature on the swimming ability of the endangered green turtle. Credit: Nick Holmes

The moment they break open the shells their mother laid them in, baby green turtles face arguably the most dangerous journey of their lives. Despite spending most of their time out in the open sea, these endangered creatures are born from clutches of eggs in deep nests in coastal and island sand dunes. Though it may take them several weeks to dig their way out of the sand, once they emerge, they rapidly plunge into the sea, and then swim continuously for about another 24 hours. On that voyage, they must run the gauntlet of hungry fish, who are thought to eat three in ten hatchling green turtles on average.

Last week, the University of Queensland’s David Booth and Andrew Evans showed that a hotter climate would harm the baby green turtles’ ability to swim away from this early death. That’s despite warmer seas improving their swimming ability. “We also found that hatchlings that emerged from cooler nests had a better swimming performance,” Booth told Simple Climate. “However the effect of nest temperature was greater than the effect of the change in water temperature. We predicted that if there were both a 2ºC rise in nest temperature and water temperature, there would be a net decrease in green turtle hatchling swimming performance, thus increasing the chances that hatchlings would be eaten by predatory fish.” Read the rest of this entry »

Simple Climate poll part 4: The effects of change

A cloud forest habitat in southern Peru where lizard species are found. Certain lizards in these habitats are at risk of extinction due to climate warming. Credit: Ignacio De la Riva.

A cloud forest habitat in southern Peru where lizard species are found. Certain lizards in these habitats are at risk of extinction due to climate warming. Credit: Ignacio De la Riva.

The impact that climate change will have on the world is what makes it such a crucial issue, and makes it important to understand. Consequently, when I have asked scientists what the situation is with climate change this year, some have given me an explanation based on the effects that they’ve seen or expect.

I’ve gathered these answers together as the last group of explanations that I’m summarizing in the Simple Climate end of year polls. These polls are a way for you to help me with one of the aims of my blog – producing a single, simple explanation of climate change. Please read them and then vote for your favourite and/or comment at the end. Also, if you haven’t already voted in them, the first three polls are still ongoing. The first includes direct explanations of the physics underlying climate change, the second one-line and metaphorical explanations, and the third includes attempts to explain it at a personal level. The winner from each poll will then go into a final poll-to-end-all-polls at the end of the year. Happy voting! Read the rest of this entry »

Coral and chatting climate: Tougher than they seem

University of British Columbia's Professor Simon Donner

University of British Columbia's Professor Simon Donner

Simon Donner says that in 30 to 50 years, if they do not adapt, we will see corals bleaching and starving dangerously frequently as the oceans warm up. “Corals, the stationary animals that build reefs, get most of their food from colourful algae which live in the coral tissue,” the University of British Columbia professor explained. “When the surrounding waters gets too hot, the corals expel the algae and lose pigmentation. If the heat stress persists, the corals can essentially starve to death.”

Donner points out that the levels of greenhouse gases already in the atmosphere today will create enough warming for this to happen by themselves – a situation he calls “committed warming”. “Even if we froze the greenhouse gas concentrations in the atmosphere today, the climate is going to keep warming for several decades,” he says. However, talking at a conference back in February, he also looked at how corals will adapt to temperature, citing some studies showing that they can increase their temperature tolerances by as much as 1.5°C. Read the rest of this entry »