By Lauri Myllyvirta and Sunil Dahiya
An economic slowdown, renewable energy growth and the impact of Covid-19 have led to the first year-on-year reduction in India's CO2 emissions in four decades. Emissions fell by around 1% in the fiscal year ending March 2020, as coal consumption fell and oil consumption flatlined.
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By Daisy Dunne
Deadly "day-night hot extremes" are increasing across the northern hemisphere due to climate change, a new study finds.
Day and Night<p>The new study, published in <a href="https://nature.com/articles/s41467-019-14233-8" target="_blank">Nature Communications</a>, looks specifically at "compound hot extremes" — a 24-hour period in summer where hot daytime temperatures are followed by similar nightime temperatures. (Temperatures are considered "hot" if they are in the top 10% of temperatures experienced by a region from 1960-2012.)</p><p>These kinds of events pose a particularly high danger to human health, explain study authors <a href="https://www.ipcc.ch/people/yang-chen/" target="_blank">Dr Yang Chen</a>, a climate extremes scientist from the <a href="http://www.cma.gov.cn/en2014/aboutcma/organizational/InstitutionsunderCMA/201409/t20140915_261139.html" target="_blank">Chinese Academy of Meteorological Sciences</a>, and <a href="https://www.researchgate.net/profile/Jun_Wang272" target="_blank">Dr Jun Wang</a>, a climate and meteorological scientist from the <a href="http://english.iap.cas.cn/" target="_blank">Institute of Atmospheric Physics</a> in China. In a joint interview, they tell Carbon Brief:</p><blockquote>Simply put, compound hot extremes deprive humans of the valuable chance of relief, which could have been provided by the 'cooling-off' effects of a nighttime low.<br></blockquote><p>Such conditions occurred during the <a href="https://www.carbonbrief.org/study-links-heatwave-deaths-london-paris-climate-change" target="_blank">2003 summer heatwave</a> in Europe, which saw <a href="https://www.sciencedirect.com/science/article/pii/S1631069107003770" target="_blank">70,000 deaths</a> across 16 countries, the authors say. Another example is the <a href="https://www.chicagomag.com/Chicago-Magazine/July-2015/1995-Chicago-heat-wave/" target="_blank">1995 Chicago heatwave</a>, which led to more than 700 heat-related deaths in just five days.<br></p><p>The study is the first to present "a complete storyline on compound hot extremes" — investigating how they have changed, the role of climate change in this and how they might increase in the future, the authors say.<br></p><p>The results show that compound hot extremes "are significantly increasing and will continue to increase in frequency and intensity" across the northern hemisphere, say Chen and Wang:</p><blockquote>These increases in heat hazards will translate into several-fold increases in population exposure to them. The rise of anthropogenic emission of greenhouse gas emissions is to blame for these increases.<br></blockquote>
Burning Up<p>For the first part of their study, the authors analysed the "fingerprint" of human-caused climate change on compound hot extremes to date. To do this, they conducted an "<a href="https://www.carbonbrief.org/category/science/extreme-weather/attribution" target="_blank">attribution</a>" analysis.<br></p><p>This involves using <a href="https://www.carbonbrief.org/qa-how-do-climate-models-work" target="_blank">climate models</a> to produce two sets of simulations: one including <a href="https://www.carbonbrief.org/analysis-why-scientists-think-100-of-global-warming-is-due-to-humans" target="_blank">all the factors that affect the climate</a>, including human-caused greenhouse gas emissions, volcanic eruptions and solar variability, and one including all of these factors except for greenhouse gas emissions.</p><p>The researchers then compared the frequency and intensity of compound hot extremes in both of these scenarios.</p><p>They found that only the scenario including human-caused greenhouse gas emissions could closely reproduce the pattern of compound hot extremes observed from 1960 to 2012. In their research paper, the authors write:</p><blockquote>We find that the summer-mean warming over 1960-2012 largely dictates the past increases in frequency and intensity of compound hot extremes during that period in both observations and simulations.<br></blockquote><p>The maps below show observed changes in summertime compound hot extreme frequency (left) and intensity (right) across the northern hemisphere from 1960-2012.</p><p>The left-hand map shows changes in the number of compound hot extreme days per decade (yellow to red for increases; light to dark blue for decreases), while the right-hand map shows changes in the average temperature of compound hot extremes per decade (same color scale).</p>
Contributions from changing temperature mean and variability. Wang et al. (2020)<p>The map shows that increases in the frequency and intensity of compound hot extremes are widespread across the northern hemisphere, with parts of continental Europe and China particularly affected.</p><p>(Gaps in the data prevented the researchers from analysing changes in the most southern parts of the northern hemisphere, the authors say in their research paper.)</p><p>While the global pattern of increases is best explained by human-caused global warming, it is possible that some regional differences may be explained by other factors, the authors say.</p><p>For example, the drying of soils could help to explain local variation of heat extremes, the authors say in their research paper.</p><p>This is because dry soils accumulate heat during the day and release it at night, Wang and Chen say, making night hot extremes and, therefore, compound hot extremes, more likely.</p>
Furnace Forecast<p>The authors also used climate models to project possible future changes to compound hot extremes until 2100. They investigated two scenarios: one "<a href="https://link.springer.com/article/10.1007/s10584-011-0148-z" target="_blank">intermediate mitigation</a>" pathway with moderately high greenhouse gas emissions ("<a href="https://link.springer.com/article/10.1007/s10584-011-0151-4" target="_blank">RCP4.5</a>") and one with very high greenhouse gas emissions ("<a href="https://www.carbonbrief.org/explainer-the-high-emissions-rcp8-5-global-warming-scenario" target="_blank">RCP8.5</a>").</p><p>Within each emissions scenario, they also looked at the changes to compound hot extremes expected if the world reaches 1.5 C and 2 C of global warming, which are the temperature limits set by the <a href="https://www.carbonbrief.org/interactive-the-paris-agreement-on-climate-change" target="_blank">Paris agreement</a>.</p><p>The charts below show the average expected change in the number of summertime compound hot extreme days (purple line), as well as independent hot days (blue line) and independent hot nights (turquoise line) across the northern hemisphere under RCP4.5 (top) and RCP8.5 (bottom) until 2100. (Compound extremes are where a hot day is followed by a hot night, whereas an "independent hot day" is when a hot day is not followed by a hot night.)</p><p>On the charts, red circles point out when the temperature limits of 1.5 C and 2 C will be breached in each scenario. The bottom chart also highlights when 4C could be breached. The various data points represent results from different climate models.</p><p>(It is worth noting that events are considered to be compound or independent. So, a 24-hour period where a hot day is followed by a hot night would be considered a compound extreme, but not an independent hot day or hot night.)</p>
Constrained projections of summertime hot extremes. Wang et al. (2020)<p>The results show that the average number of compound hot extreme days across the northern hemisphere in summer would more than double if temperatures reach 2 C, when compared to 2012.</p><p>Keeping temperatures at 1.5 C could see five fewer compound hot extreme days across the northern hemisphere, on average, when compared to 2 C, the research adds.</p><p>If greenhouse gas emissions are extremely high (RCP8.5), the number of summertime compound hot extremes could increase eight-fold by 2100, when compared to 2012, the results show.</p><p>The charts also show that compound hot events are expected to increase at a much more rapid rate than independent hot day or hot night events.</p><p>This is chiefly because <a href="https://www.nytimes.com/interactive/2018/07/11/climate/summer-nights-warming-faster-than-days-dangerous.html" target="_blank">climate change is known</a> to have a larger effect on nightime temperatures than daytime temperatures, the authors say.</p><p>Therefore, as the chances of hot nights become higher, the chances of compound hot events also increase — and, so, the chances of a hot day or night occurring independently decreases, explain Chen and Wang.</p>
‘Clear Evidence’<p>The findings reinforce "the urgency in reducing emission of greenhouse gases" for policymakers, say Chen and Wang:</p><blockquote>We should keep the point in mind that as the globe warms, future summers are increasingly dominated by compound hot extremes and become more uncomfortable. Namely, a hot day accompanied by a hot night without a relief window for humans might become a 'new norm'. As a result, vigilance against excess heat should be kept through day and night.<br></blockquote><p>The study is "impressively comprehensive," says <a href="http://www.bristol.ac.uk/geography/people/eunice-t-lo/overview.html" target="_blank">Dr Eunice Lo</a>, a research associate in climate extremes from the <a href="https://www.bristol.ac.uk/" target="_blank">University of Bristol</a>, who was not involved in the research. She tells Carbon Brief:</p><blockquote>I think the main take home message from this study is that we should use consecutive day-night hot extremes as a major heat-health indicator for policymaking, as compound hot extremes are projected to have larger future increases in frequency and intensity then hot days or nights.<br></blockquote><p>The findings produce "clear evidence" that human-caused climate change is leaving its mark on extreme heat events, says <a href="https://www.metoffice.gov.uk/research/people/peter-stott" target="_blank">Prof Peter Stott</a>, who leads on climate monitoring and attribution at the <a href="https://www.metoffice.gov.uk/weather/climate-change/organisations-and-reports/met-office-hadley-centre" target="_blank">Met Office Hadley Centre</a>. Stott, who was also not involved in the research, tells Carbon Brief:</p><blockquote>I don't find the conclusions of the study very surprising, but I do like the way the authors have comprehensively set out the implications – the clear evidence that the changes to date are driven by human emissions and the clear evidence that future changes will result in significant increases in the frequency and intensity of these compound extremes worldwide.<br></blockquote>
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By Simon Evans
Renewable sources of electricity are set for rapid growth over the next five years, which could see them match the output of the world's coal-fired power stations for the first time ever.
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By Simon Evans
During the three months of July, August and September, renewables generated an estimated total of 29.5 terawatt hours (TWh), compared with just 29.1TWh from fossil fuels, the analysis shows.
Transformative Decade<p>At the start of this decade in 2010, the 288TWh generated from fossil fuels accounted for around three-quarters of the UK total. It was also <a href="http://interactive.carbonbrief.org//how-uk-transformed-electricity-supply-decade/#" target="_blank">more than 10 times</a> as much electricity as the 26TWh that came from renewables.</p><p>Since then, electricity generation from renewable sources has more than quadrupled – and <a href="https://www.carbonbrief.org/analysis-uk-electricity-generation-2018-falls-to-lowest-since-1994" target="_blank">demand has fallen</a> – leaving fossil fuels with a shrinking share of the total.</p><p>This shift is shown in the chart below, with the declining quarterly output from power stations burning coal, oil and gas in blue and rising generation from renewables in red.</p><p>(The quarterly chart also reflects the seasons, with demand higher in winter and lower in summer. Wind farm output is well matched with this cycle, as it tends to be windier in winter.)</p><iframe scrolling="no" frameborder="0" marginheight="0px" marginwidth="0px" style="display: initial; margin: 0 auto;" src="https://cbhighcharts2019.s3.eu-west-2.amazonaws.com/q3-2019-electricity/renewables-beating-fossil-fuels-uk.html" width="800px" height="550px"></iframe><span style="display:block; height:22px; max-width:800px;"><img src="https://s3.eu-west-2.amazonaws.com/cbhighcharts2019/cb-logo-highcharts.svg" style="width: 22px; height: 22px; margin-top: 2px; margin-bottom: 2px; float:right; background-repeat: no-repeat; background-size: contain;"/></span>
New Capacity<p>Over the past year, the most significant reason for rising renewable generation has been an increase in capacity as new offshore wind farms have opened. The 1,200 megawatt (MW) Hornsea One project <a href="https://www.powerengineeringint.com/2019/10/04/final-turbines-installed-at-hornsea-1/" target="_blank">was completed</a> in October, becoming the world's largest offshore wind farm. The 588MW Beatrice offshore wind farm was completed in <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/835114/Renewables_September_2019.pdf" target="_blank">Q2 of this year</a>.</p><p>These schemes add to the <a href="https://www.renewableuk.com/page/UKWEDSearch" target="_blank">more than 2,100MW</a> of offshore capacity that started operating during 2018. Further capacity is already being built, including the 714MW East Anglia One project that <a href="https://www.offshorewind.biz/2019/09/12/east-anglia-one-generates-first-power/" target="_blank">started generating electricity</a> this year and will be completed in 2020.</p><p>In total, government contracts for offshore wind will take capacity from nearly 8,500MW today to around 20,000MW by the mid-2020s. The government and industry are jointly aiming for at least 30,000MW of offshore wind capacity by 2030, with two further contract auctions already expected.</p><p>In September, the latest auction round produced <a href="https://www.carbonbrief.org/analysis-record-low-uk-offshore-wind-cheaper-than-existing-gas-plants-by-2023" target="_blank">record-low deals</a> for offshore wind farms that will generate electricity more cheaply than expected market prices – and potentially below the cost of running existing gas plants.</p><p>Other contributors to the recent increase in renewable generation include the opening of the 420MW Lynemouth biomass plant in Northumberland last year and the addition of hundreds of megawatts of new onshore wind and solar farms. (Another new 299MW biomass plant being built on Teesside, with a <a href="https://www.gazettelive.co.uk/news/teesside-news/hundreds-laid-tees-energy-plant-16669866" target="_blank">scheduled opening</a> in early 2020, is <a href="https://www.gazettelive.co.uk/news/teesside-news/unite-demands-urgent-answers-after-16723624" target="_blank">facing "major delays"</a>.)</p><p>According to the <a href="https://www.gov.uk/government/organisations/department-for-business-energy-and-industrial-strategy" target="_blank">Department of Business, Energy and Industrial Strategy</a> (BEIS), the rise in renewable output during the <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/835114/Renewables_September_2019.pdf" target="_blank">first</a> <a href="https://web.archive.org/web/20190724204007/https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/811971/Electricity_June_2019.pdf" target="_blank">half</a> of 2019 was down to these increases in capacity, with weather conditions not unusual for the time of year.</p>
Consecutive Months<p>Carbon Brief's electricity-sector analysis shows that renewables are also estimated to have generated more electricity than fossil fuels during the individual months of August and September, the first time there have been two consecutive such months.</p><p>Previously, renewables beat fossil fuels in September 2018 – the first-ever whole month – and then again in March 2019. This means that there have only ever been four months where renewables outpaced fossil generation, of which three have been this year and two in the last two months.</p><p>This is shown in the chart, below, which also highlights the greater month-to-month variability in electricity generation and demand, which is overlaid on top of the broader seasonal cycles.</p><iframe scrolling="no" frameborder="0" marginheight="0px" marginwidth="0px" style="display: initial; margin: 0 auto;" src="https://cbhighcharts2019.s3.eu-west-2.amazonaws.com/q3-2019-electricity/renewables-fossils-monthly.html" width="800px" height="550px"></iframe><span style="display:block; height:22px; max-width:800px;"><img src="https://s3.eu-west-2.amazonaws.com/cbhighcharts2019/cb-logo-highcharts.svg" style="width: 22px; height: 22px; margin-top: 2px; margin-bottom: 2px; float:right; background-repeat: no-repeat; background-size: contain;"/></span>
Methodology<p>The figures in the article are from Carbon Brief analysis of data from <a href="https://www.gov.uk/government/statistics/electricity-section-5-energy-trends" target="_blank">BEIS Energy Trends chapter 5</a> and <a href="https://www.gov.uk/government/statistics/energy-trends-section-6-renewables" target="_blank">chapter 6</a>, as well as from <a href="https://www.bmreports.com/" target="_blank">BM Reports</a>. The figures from BM Reports are for electricity supplied to the grid in Great Britain only and are adjusted to include Northern Ireland.<br></p><p>In Carbon Brief's analysis, the BM Reports numbers are also adjusted to account for electricity used by power plants on site and for generation by plants not connected to the high-voltage national grid. This includes many onshore wind farms, as well as industrial gas combined heat and power plants and those burning landfill gas, waste or sewage gas.</p><p>By design, the Carbon Brief analysis is intended to align as closely as possible to the official government figures on electricity generated in the UK, reported in <a href="https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/834120/ET_5.1.xls" target="_blank">BEIS Energy Trends table 5.1</a>. Briefly, the raw data for each fuel is adjusted with a multiplier, derived from the ratio between the reported BEIS numbers and unadjusted figures for previous quarters.</p><p>Carbon Brief's method of analysis has been verified against published BEIS figures using "<a href="https://www.definitions.net/definition/HINDCAST" target="_blank">hindcasting</a>". This shows the estimates for total electricity generation from fossil fuels or renewables to have been within ±3% of the BEIS number in each quarter since Q4 2017. (Data before then is not sufficient to carry out the Carbon Brief analysis.)</p><p>For example, in the second quarter of 2019, a Carbon Brief hindcast estimates gas generation at 33.1TWh, whereas the published BEIS figure was 34.0TWh. Similarly, it produces an estimate of 27.4TWh for renewables, against a BEIS figure of 27.1TWh.</p><p>The Carbon Brief estimated totals for fossil fuels and renewables are very close in Q3 2019, coming within 0.5TWh of each other. This means that despite the relatively low level of uncertainty in the estimates, their relative position could be reversed in the official BEIS data.</p><p>This serves to emphasize the fact that the broader trend of decline for fossil fuels and an increase for renewables is of far greater significance than the precise figures for any individual quarter.</p><p>In contrast to Carbon Brief's analysis, figures published by consultancy <a href="https://www.enappsys.com/" target="_blank">EnAppSys</a> for the third quarter of 2019 <a href="https://docs.wixstatic.com/ugd/42d1d7_05a6259d8486422e9783a3d852bb4537.pdf" target="_blank">suggest that</a> fossil fuels generated slightly more electricity than renewables. There are several reasons for this difference.</p><p>First, the company's analysis is for Great Britain only, whereas Carbon Brief's covers the UK overall. Second, it reports on electricity "supplied" in the country, including imports, whereas Carbon Brief estimates the amount of electricity "generated" within the UK only.</p><p>Third, Carbon Brief's analysis is, by design, aligned with the quarterly <a href="https://www.gov.uk/government/collections/energy-trends" target="_blank">BEIS Energy Trends</a> data for electricity generation, whereas EnAppSys uses its own approach.</p><p>For comparison, <a href="https://docs.wixstatic.com/ugd/42d1d7_3ffce1328967400f97678b53bc4e8b55.pdf" target="_blank">EnAppSys reported</a> for the second quarter of 2019 that 28.3TWh was supplied in GB from gas, whereas <a href="https://www.gov.uk/government/statistics/electricity-section-5-energy-trends" target="_blank">BEIS reports</a> that 34.0TWh was generated in the UK. Similarly EnAppSys reported 23.1TWh coming from renewables, against a BEIS figure of 27.1TWh.</p>
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By Josh Gabbatiss
Chart showing the historical levelized cost of electricity (LCOE) from solar power in China.
Source: Yan et al. (2019)
By Simon Evans
Machines that suck CO2 directly from the air could cut the cost of meeting global climate goals, a new study finds, but they would need as much as a quarter of global energy supplies in 2100.
Global CO2 emissions from fossil fuels (Gt/yr) in model pathways consistent with limiting warming this century to 1.5 C (left panel, blue) or 2 C (right panel, green). Results from two different IAMs – TIAM and WITCH – are shown with solid and dashed lines, respectively. The various lines show scenarios that use direct capture ("DAC," darker shades) and those that do not ("NoDAC," lighter), as well as pathways to 2 C without negative emissions of any sort ("NoNET," darkest green). Source: Realmonte et al. (2019).
Climeworks greenhouse © Climeworks / Julia Dunlop
By Zeke Hausfather
This has raised the question of what role, if any, climate change may have played in this unusually intensive period of tornadoes. While some have suggested that climate change is driving the above-average numbers, the scientific community has pushed back on these claims.
Understanding and attribution of climate change impacts on extreme events, by event type.
Figure from the U.S. National Academy of Sciences report on the Attribution of Extreme Weather Events published in 2016.
U.S. tornado tracks by Fujito scale severity (F0-F5) from 1950-2016.
Image from usatornadoes.com.
Number of days with at least one F1+ tornado (black) and over 30 F1+ tornadoes (grey) between 1950 and 2014.
Figure 4 in Brooks et al 2014.
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By Jocelyn Timperley
Global transport emissions could peak in the 2030s if railways are "aggressively" expanded, said the International Energy Agency (IEA).
By Daisy Dunne
Methane emissions from coal mining in China have risen despite stricter government regulations that aimed to curb the greenhouse gas, satellite data shows.
By Daisy Dunne
The IEA's Coal 2018 report finds that global coal demand grew by 1 percent in 2017 after two years of decline. The rise was chiefly driven by global economic growth, it says. Despite recent growth, demand is still below "peak" levels seen in 2014.
Demand is likely to "remain stable" until 2023, the report authors say. This is because falling demand in western Europe and North America is likely to be offset by increased demand in a host of Asian countries, including India, Indonesia and Vietnam.
Carbon Brief takes a look at the IEA's changing coal forecasts for key world regions.
By Daisy Dunne
Spraying aerosols high in the stratosphere could dampen global warming over land, but may not prevent the oceans from heating up, new research says.
By Robert McSweeney
Arctic sea ice has reached its summer minimum extent for the year, clocking in at 4.59m square kilometers (sq km) (approximately 1.77m square miles), which puts it joint sixth lowest in the 40-year satellite record alongside 2008 and 2010.
The twelve smallest summer lows in the satellite record have all occurred in the last twelve years.
By Daisy Dunne
Restricting global warming to 2°C above pre-industrial levels would prevent large increases in temperature-related deaths across much of the globe, a new study finds.
And keeping warming to 1.5°C—the aspirational target of the Paris agreement—would further limit the number of people dying from temperature extremes in some parts of the world, including in southeast Asia and southern Europe.