New Delhi: The effectiveness of an important mosquito-fighting insecticide may be impaired by global warming, according to a recent study.
Two researchers from Montana State University, graduate student Shavonn Whiten and Robert Peterson, have shown that permethrin becomes less effective at killing the yellow fever mosquito (Aedes aegypti) as temperatures increase.
These mosquitoes, which are found in the tropics and the subtropics, can transmit viruses that lead to dengue, chikungunya, yellow fever, and other diseases.
“Many of the areas where these insecticides are employed have varying drastic temperature changes,” Shavonn Whiten said.
The researchers exposed adult mosquitoes to varying concentrations of permethrin at a range of temperatures.
They found an inverse relationship between death and temperature from 16 AoC to 30 AoC, which showed the highest negative correlation.
From 30 to 32, there was, however, a positive correlation between mortality and temperature. And from 32 to 34, the negative correlation resumed.
“It probably has something to do with variability and heat stress,” said Peterson.
“Once you get to those higher temperatures, there are other things going on regarding stress on the mosquito that cancel out the effect of the pyrethroids (a class of pesticides to which permethrin belongs) working better at lower temperatures and worse at higher temperatures,” he explained.
People involved in mosquito-control efforts should take temperature into account when choosing a pest control product, researchers said. The study was published in the Journal of Medical Entomology.
Last-ditch efforts to hold climate change to the most ambitious target set by governments will likely require using every available technique rather than picking and choosing the most attractive ones, climate scientists said on Monday.
Dramatically reducing the use of coal, planting huge swaths of land with carbon-absorbing forest or powering most transport with electricity are no longer sufficient to bring about the swift transition needed, they said, with warming expected to pass the 1.5 degree Celsius (2.7 degrees Fahrenheit) mark in as little as 12 years.
“We can make choices about how much of each option to choose, but the idea you can leave anything out is impossible,” said Jim Skea, who jointly led a major scientific report analyzing the feasibility of holding global average temperature rise to 1.5 degrees C above pre-industrial levels, the most ambitious goal of the 2015 Paris Agreement.
The Intergovernmental Panel on Climate Change (IPCC) report, requested by governments, was issued ahead of a U.N. conference in December in Poland that will consider how to increase country ambitions to cut emissions and manage climate risks better.
Current government commitments to curb climate change under the Paris pact, even if fully met, would still leave the world on track for about 3 degrees of warming, scientists said.
To have a chance of meeting the 1.5 degrees goal, climate-changing emissions would have to plunge 45 percent by 2030 compared to 2010 levels, the report said.
As that would be an “unprecedented” rate of decline, it is more likely the world will overshoot the target, then try to return to it by sucking carbon from the air, scientists said.
Such “carbon removal” might happen by developing better technology to take out carbon dioxide from the atmosphere – now an extremely expensive process – or by planting many more forests that could be harvested and burned for energy, with emissions pumped into underground storage.
“We have not identified any pathways that get to 1.5 degrees Celsius without some kind of carbon dioxide removal,” Skea said.
But turning over much more land for energy production “could have implications for food security, ecosystems and biodiversity,” the British scientist warned, as competition for land grows.
All on board
Swiftly reducing emissions – even with carbon removal – will also require unprecedented levels of international cooperation, a particular challenge as some national governments, like that in the United States, look increasingly inward.
Making the needed emissions changes “is within the scope of what humans can achieve”, said Hans-Otto Portner, a German climate scientist and IPCC report co-chair.
But success “depends on political leadership,” he added.
Henri Waisman, a senior researcher at Paris-based think tank IDDRI and one of 91 report authors, said the report’s aim was to set out the types of transformation required as clearly as possible to inform discussions at U.N. climate talks and beyond.
Delaying action on climate change “is something that is explicitly contradicted in the report,” he told the Thomson Reuters Foundation.
If governments fail to ramp up their ambition to reduce heat-trapping emissions over the next two years, they will have consciously abandoned the 1.5 degree goal, he added.
Action in cities – which consume more than two-thirds of energy globally and account for about three-quarters of carbon emissions – are pivotal to meeting the target, said report author William Solecki, a professor at Hunter College-City University of New York.
That’s particularly true because most population growth in coming years “is going to be in urban areas – a lot of it particularly in small and medium-sized cities … in the global south,” he said.
Those cities will need more support to develop cleanly, prevent disasters and adapt to climate shifts, he added.
The scientists said the report was intended to guide more than just governments, however, and that action by everyone – including individuals and businesses – would be required to hold the line on climate change.
“There’s a lot we can do individually or within our communities,” said Debora Ley, a report author who works on adaptation and renewable energy in Latin America.