Scientists Solve Climate Hiatus 'Puzzle of the Century': So Now What?
By Tim Radford
They say they now know why computer simulations and the forecasts made by a study of the historical record don't seem to agree.
The good news is that scholarly conflict may have been resolved. The bad news is that, if carbon dioxide levels in the atmosphere are permitted to double, then the average global temperatures could reach 4.5°C by the century's end, or even up to 6°C.
The debate may seem entirely academic, if only because 197 nations of the world undertook to contain global warming to "well below" 2°C by the end of the century by drastically reducing the consumption of fossil fuels.
But collectively, the national plans so far proposed do not look likely to meet this target, and the U.S. has threatened to withdraw from the undertaking anyway. So there remains a "what-if" case to settle a long-standing conflict.
And the conflict is this: examine the earth's climate over millions of years, and reconstruct greenhouse gas levels, and you get a prediction that says if carbon dioxide in the atmosphere—for most of human history it has been 280 parts per million—doubles, then the average global temperatures will rise by between 1.5°C and 4.5°C. Use computer simulations, and you get much the same result.
But when you examine the results of temperature measurements taken since the thermometer was invented, and extrapolate, the answer is a bit different: 1°C to 3°C.
A new study in the journal Science Advances proposes a simple solution: the predictions based on recent historical evidence do not take into account all the natural cycles of long-term warming and cooling. Factor those in, and the circle can be squared.
Research like this offers a glimpse of science in action. Scientists are never happy when prediction and observation don't match. For years, they have worried away at what has become known as the "so-called hiatus" or apparent pause in the rate of global warming in the first dozen or so years of this century.
In fact the world continued to warm, but the rate of warming was significantly slower than that measured in the last two decades of the 20th century.
Some argued that the world had warmed, but all the heat had gone into the oceans. Others argued that any apparent slowdown could only be fleeting and global warming would accelerate again. Yet a third school maintained that the pause was entirely illusory, and that even if there was a pause it would have no effect on long-term predictions.
These competing explanations were in themselves evidence that the mismatch of data and prediction bothered the climate boffins.
For much the same reason, researchers have tried to find what might be called the extreme hypothetical limits to climate change: for instance, could carbon dioxide levels fall so low the planet would entirely freeze? (The answer is, so far, no).
Could the greenhouse gas levels get so high that the oceans could boil dry? The answer is, in theory yes: the earth could become up to 60°C hotter than it is now, and uninhabitable, but mercifully, only in theory.
So the outcome of the latest study is an academic confirmation that different patterns and rates of warming play into the big picture. Land, for instance, warms faster than ocean. Most of the land surface of the planet is in the northern hemisphere. So there is a good reason why global warming is, or seems, uneven.
"The historical pattern of warming is that most of the warming has occurred over land, in particular over the northern hemisphere," said Cristian Proistosescu, who made the study at Harvard University.
"This pattern of warming is known as the fast mode—you put CO2 in the atmosphere and very quickly after that, the land in the northern hemisphere is going to warm."
But the warming of the Southern Ocean, swirling around Antarctica, and the Eastern Equatorial Pacific proceed at a different pace, and with changes in cloud cover which complicate the calculations. So Proistosescu and his co-author worked on the mathematics necessary to resolve their little local difficulty.
"The models simulate a warming pattern like today's, but indicate that strong feedbacks kick in when the Southern Ocean and Eastern Equatorial Pacific eventually warm, leading to higher overall temperatures than would simply be extrapolated from the warming seen to date," said Peter Huybers, an earth and planetary scientist at Harvard, and the other author.
The message is that the slow mode matters, but only in the long term. What can be measured now, and recently, does not necessarily indicate how things will end up eight decades on.
"Historical observations give us a lot of insight into how climate changes and are an important test of our climate models," said Huybers, "but there is no perfect analogue for the changes that are coming."
Reposted with permission from our media associate Climate News Network.
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By Matt Kasson, Brian Lovett and Carolee Bull
Home gardening is having a boom year across the U.S. Whether they're growing their own food in response to pandemic shortages or just looking for a diversion, numerous aspiring gardeners have constructed their first raised beds, and seeds are flying off suppliers' shelves. Now that gardens are largely planted, much of the work for the next several months revolves around keeping them healthy.
Start With Prevention<p>Just as preventive steps like maintaining a balanced diet help keep humans healthy, home growers can take many actions to help their gardens thrive.</p><p>One key step is assessing soil fertility – the ability of soil to sustain plant growth – which can vary widely depending on your location and soil type. Low soil fertility limits food production and predisposes plants to disease and pests. University extension <a href="https://soiltesting.wvu.edu/" target="_blank">soil testing labs</a> can help evaluate the quality of garden soil and identify nutrient deficiencies and acidic soils, often at no charge.</p>
Using weed barrier landscape cloth for planting rows and mulching between rows is an effective way to suppress weeds. Matt Kasson, CC BY-ND
Diagnosing Problems<p>Common plant pathogens include <a href="https://www.apsnet.org/edcenter/disandpath/viral/introduction/Pages/PlantViruses.aspx" target="_blank">viruses</a>, <a href="https://www.apsnet.org/edcenter/disandpath/prokaryote/intro/Pages/Bacteria.aspx" target="_blank">bacteria</a>, <a href="https://www.apsnet.org/edcenter/disandpath/nematode/intro/Pages/IntroNematodes.aspx" target="_blank">nematodes</a>, <a href="https://www.apsnet.org/edcenter/disandpath/oomycete/introduction/Pages/IntroOomycetes.aspx#:%7E:text=The%20oomycetes%2C%20also%20known%20as,foliar%20blights%20and%20downy%20mildews." target="_blank">oomycetes</a> and <a href="https://www.apsnet.org/edcenter/disandpath/fungalasco/intro/Pages/IntroFungi.aspx" target="_blank">fungi</a>. All of these microorganisms, especially at an early stage of infection, are too small to see. But when they proliferate, they cause changes in plants that we can recognize.</p><p>Unlike insects, which move around on six legs or on wings through the air, pathogens can move unseen and unchecked from leaf to leaf on the wind, through the soil or in droplets of water. Some microbes have even formed intimate relationships with insects and use them as vehicles to move from plant to plant, which makes these pathogens even more challenging to manage. Unfortunately, by the time some pathogens make their presence known, the damage is already done.</p><p>We recently conducted a <a href="https://twitter.com/kasson_wvu/status/1265989041725624323" target="_blank">Twitter poll</a> of gardeners nationwide to find out which culprits plagued their gardens. People named <a href="https://ento.psu.edu/extension/factsheets/aphids" target="_blank">aphids</a>, <a href="https://ento.psu.edu/extension/factsheets/squash-vine-borer" target="_blank">squash vine borers</a>, <a href="https://ento.psu.edu/extension/factsheets/squash-bug" target="_blank">squash bugs</a> and <a href="https://ento.psu.edu/extension/factsheets/flea-beetle" target="_blank">flea beetles</a> as the most problematic insect pests. Their most troublesome pathogens included <a href="https://extension.wvu.edu/lawn-gardening-pests/plant-disease/fruit-vegetable-diseases/powdery-mildew" target="_blank">powdery mildew</a>, <a href="https://plantpath.ifas.ufl.edu/rsol/Trainingmodules/BWTomato_Module.html" target="_blank">tomato bacterial wilt</a> and <a href="https://extension.wvu.edu/lawn-gardening-pests/plant-disease/fruit-vegetable-diseases/downy-mildew" target="_blank">cucurbit downy mildew</a>.</p><p>To manage such perennial challenges, the first step is to spend time closely looking at your plants. Do you notice any insects consistently hanging around, or molds colonizing leaves or other plant parts? How about symptoms such as blight, stunting, or leaves that are yellowing, browning or wilting?</p>
This white fungal growth is an early sign of powdery mildew on a leaf of susceptible summer squash. Matt Kasson, CC BY-ND
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The effects of climate change may more far-reaching than you think.
Hotter temperatures have been linked to a rise in energy poverty, with more people struggling to meet their energy bills from their household income, according to a new study published on ScienceDirect by researchers from Italy's Ca' Foscari University.
Value of air conditioning imports in selected OECD countries. ScienceDirect
The ‘Golden Thread’<p>The <a href="https://www.endenergypoverty.org/reports" target="_blank">Global Commission to End Energy Poverty</a> calls access to energy the "golden thread" that weaves together economic growth, human development, and environmental sustainability. And one of the <a href="https://www.weforum.org/agenda/archive/sdg-07-affordable-and-clean-energy" target="_blank">United Nations' Sustainable Development Goals</a> is to ensure access to affordable, reliable, sustainable and modern energy for all by 2030.</p><p>Sustainability also has a large role to play in the future of energy and failing to embed green policies in COVID-19 stimulus packages and underinvesting in green infrastructure are current risks, according to the <a href="http://www3.weforum.org/docs/WEF_COVID_19_Risks_Outlook_Special_Edition_Pages.pdf" target="_blank">World Economic Forum</a>.</p><p>In its vision for a 'Great Reset' – building a better world after the pandemic – the Forum and the IMF jointly backed the <a href="https://www.weforum.org/agenda/2020/06/end-fossil-fuel-subsidies-economy-imf-georgieva-great-reset-climate/" target="_blank">transition to a green economy</a> and called for an end to fossil fuel subsidies.</p>
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Scores of people remained stranded in southern Japan on Sunday after heavy rain the day before caused deep flooding and mudslides that left at least 34 people confirmed or presumed dead.
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