Predicting lead contamination

Amid reignited fears about lead poisoning in the US, the key to identifying solutions could lie in the common city pigeon. A study published Monday in the journal Chemosphere found that New York’s Manhattan neighbourhoods that had many children with elevated blood lead levels also had pigeons with elevated lead. The research suggests that scientists may be able to use the birds to predict lead contamination in the environment.

The principal author of the study, Rebecca Calisi, examined data on 825 pigeons from various neighbourhoods from 2010-2015. Rebecca found that elevated lead levels in pigeons correlated positively with elevated lead levels in children in those neighbourhoods, as identified by New York City’s health department. The link indicates that pigeons could be used to detect areas of pollution across the country. “There’s a potential to be able to circumvent health problems in humans before they begin,” said Rebecca.

The researchers drew on data compiled by the Wild Bird Fund, a New York City non-profit organisation that rehabilitates sick, injured or orphaned birds. Rebecca recognised that pigeons would be ideal birds for making comparisons with human health, she said, because they live in proximity to people and eat much of the same food. And unlike many other birds, they tend to spend their entire lives within the same square mile. Whether the information from this study will be practically useful is up for discussion. But for Rebecca, the findings present opportunities that extend well beyond New York — and even lead. Researchers in her lab in California intend to use pigeons to monitor other heavy metals, as well as pesticides and fire retardants, in urban areas worldwide. “We’re just getting started,” Rebecca said. “This is kind of the beginning of what’s going to be a really big field of study.”

Clouds get high on climate change

Clouds are moving up, up and away. An analysis of satellite data has found that, since the early 1980s, clouds have shifted toward Earth’s poles and cloud tops have extended higher into the atmosphere. The changes match what climate models predict and are a rare step forward among much scientific uncertainty about how clouds will behave in a warming world. “It’s really the first credible evidence that we have of climate change and clouds in the observed record,” says Joel Norris, an atmospheric scientist at the Scripps Institution of Oceanography in La Jolla, California, USA. Clouds are both hard to observe and difficult to simulate in climate models, says Katherine Marvel, a climate researcher at NASA’s Goddard Institute for Space Studies in New York City, USA. This is because researchers have to cobble together data on cloud patterns from existing satellite observations.

Joel’s team tried to get around this issue by purging satellite data of misleading readings, such as those produced by sensors that have degraded over time. The scientists used two long-term databases of cloud cover, along with measures of water content over the oceans and of Earth’s reflectivity — or how much sunlight the planet’s surface throws back into space. By 2009, the team found that there were fewer clouds over the mid-latitudes than there had been in 1983. That finding meshes with climate predictions that dry zones will expand out of the subtropics and push storms toward the poles. The team also found that cloud tops rose higher in the atmosphere by the end of the 2000s, again as predicted for a warming atmosphere.

Joel and his colleagues “have done a great job using the satellite record in an appropriate way,” says Ryan Eastman, an atmospheric scientist at the University of Washington in Seattle, USA. In 2013, he and a colleague used ground-based observations of clouds to describe some of the same trends. Their study also noted that clouds were declining in middle latitudes as storms shifted poleward. The new work meshes well with the earlier findings, Ryan says. The fact that observations match the model predictions is worrying, says Veerabhadran Ramanathan, an atmospheric scientist at the Scripps Institution of Oceanography who was not in the team.

If models really are starting to get clouds correct, it suggests that the planet may warm on the higher end of estimates over the coming century, he says. Still, the story remains complicated. The cloud shifts match what scientists would expect from increasing greenhouse-gas emissions, but also what happens in the aftermath of large volcanic eruptions that spew particles into the atmosphere. Researchers need to dig a little more to tease out the relative roles of greenhouse gases and volcanoes, Katherine says. Joel aims to do that next. “The data aren’t hopeless,” he says. “There’s more here than we thought.”

Alexandra Witze