In Today’s Science News, we learn about the Sixth Assessment Report of the IPCC, how CRISPR may have the key for a cure of HIV and the toll air pollution has on tropical cities.
Article 1: IPCC’s starkest message yet: extreme steps needed
to avert climate disaster
Nature date: 5th April, 2022
Et-Date: 10th April, 2022
Summary: The Sixth Assessment Report of the IPCC was officially released on February 27th, 2022 (i.e. the final/approved version). 195 countries approved it after two-day long negotiations. In the ~2,900 pages (result of the work of hundreds of scientists across 65 countries), the focus is on curbing emissions and mitigating the effects of global warming.
Little time remains to act, however, humanity has the technology and means to achieve it.
Description of Contents
While a temporary warming above 1.5 C° might be inevitable, it is possible to bring temperatures back down if aggression action is taken to cut back on greenhouse gas emissions and extract carbon emissions from the atmosphere – according to the latest IPCC report. However, the window of opportunity is rapidly closing.
As Inger Andersen, executive director of the UN Environment Program, put it at the press conference: „But increased action must begin this year, not next year; this month, not next month; and indeed today, not tomorrow.“
In the 2,900 page long report (which is also available as a 37-page summary for policy makers and everyone who’s interested), which was the result of hundreds of scientists across 65 countries working together, the focus is on curtailing emissions and mitigating the effects of global warming. The final version was approved by 195 countries.
Multiple sources reported on difficulties during the virtual negotiations, among them India that raised questions about equity and responsibility and Saudia Arabia which scrutinized language related to the carbon-capture technology and the future of fossil fuels.
While it pushed the negotiations overtime, they neither impact the findings nor the underlying science in the report.
Now, it is up to the governments whether they will „step up to the challenge with actions rather than unfulfilled pledges“.
Key Points from the Report
- 2025 is the latest date that global emissions should peak and then decline drastically, for a 50% chance to limit warming to 1.5 °C.
In order to achieve the current goal, Co2-emissions would need to nearly halve by 2030 and reach ’net zero‘ by 2050.
Our current course – scientists estimated – puts us on a path for a 3 °C rise above pre-industrial levels,
- On a positive note: the price of renewable-energy technologies strong decreased and the global economy overall is getting cleaner.
Between 2010 and 2019, global energy intensity decreased by 2% annually – reversing a trend from the decades prior,
- In order to the reach the 1.5 °C goal, some fossil fuels must remain underground.
Models slightly above this limit say that emissions from currently existing and planned fossil fuel projects exceed it,
- Net-zero emissions cannot be achieved by reducing Co2-emissions alone, carbon dixodie extraction will also be needed,
This can be achieved by reforestation, improving agricultural practices or a variety of nascent technologies that are able to to capture carbon emissions,
- Global economic growth wouldn’t be hindered by aggressive action to curb emissions.
While the GDP is projected to shortly dip mid-century with climate policies enacted, most research suggests that the economic benefits of limiting warming outweighs the cost of mitigation,
- Wealthy countries will need to aid low-income countries financially to address inequities in vulnerability to climate change and to speed up the clean-energy transition in a way that benefits all.
Nations with the lowest amounts of greenhouse gas emissions are often those who are the most affected: the 88 countries that compromise the Least Developed Countries and Island Developing States are collectively responsible for 1% of historical carbon emission.
Article 2: CRISPR and HIV: New technique in human blood unveils potential paths toward cure
SD-Date: 1st April, 2022
Et-Date: 10th April, 2022
ScienceDaily Summary: „Scientists are using new advances in CRISPR gene-editing technology to uncover new biology that could lead to longer-lasting treatments and new therapeutic strategies for Human Immunodeficiency Virus (HIV).“
HIV still poses a threat to human health with last year alone an estimated 1.5 million new infections. Existing drug treatments are a very important tool to fight the HIV epidemic, being quite effective at suppressing viral replication and spread. However, they are only a treatment and not a cure, so people suffering from HIV have to follow a strict treatment regimen that requires continuous access to good affordable healthcare – not everyone has access to said infrastructure.
Studies before relied on immortalized human cancer cells (such as HeLa cells, the story of Henrietta Lacks can be read here and how it impacted ethics in the policy of biospecimens) as models to study how HIV replicated in the laboratory. They are easy to manipulate, but imperfect models of human blood cells. Furthermore, the majority of the studies used technology that could only turn down the expression of certain genes and not turn them off as it is with CRISPR the case, thus scientists cannot always definitely determine if a gene was involved in helping or suppressing viral replication.
The team around Judd Hultquist (a co-corresponding author) seeks to answer the question how the HIV virus – which only got 12 proteins and a genome that is a third of the size of SARS-CoV-2 – hijacks the body’s cells to replicate and spread across the system.
Method of Research
As mentioned above, for this study the gene-editing technology CRISPR/Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats) had been used. For those unfamiliar with said technology or who need to refresh their knowledge:
„To recap: in nature, when a virus invades bacteria, its unique DNA is integrated into a CRISPR sequence in the bacterial genome. This means that the next time the virus attacks, the bacteria will remember it and send RNA and Cas to locate and destroy the virus.
While there are other Cas enzymes derived from bacteria that cut out viruses when they attack bacteria, Cas9 is the best enzyme at doing this in animals. The term CRISPR-Cas9 refers to a Cas variety being used to cut animal (including human) DNA.“
(source: cbinsights, link embetted)
The explanation of CBInsights also summarizes the history of the technology. Additionally, I recommend the article of the National Library of Medicine (NIH).
„Cas9, one of the associated proteins, is an endonuclease that cuts both strands of DNA. Cas9 is directed to its target by a section of RNA. This can be synthesised as a single strand called a synthetic single guide RNA (sgRNA); the section of RNA which binds to the genomic DNA is 18–20 nucleotides. In order to cut, a specific sequence of DNA of between 2 and 5 nucleotides (the exact sequence depends upon the bacteria which produces the Cas9) must lie at the 3’ end of the guide RNA: this is called the protospacer adjacent motif (PAM). Repair after the DNA cut may occur via two pathways: non-homologous end joining, typically leading to a random insertion/deletion of DNA, or homology directed repair where a homologous piece of DNA is used as a repair template. It is the latter which allows precise genome editing: the homologous section of DNA with the required sequence change may be delivered with the Cas9 nuclease and sgRNA, theoretically allowing changes as precise as a single base-pair.“ (source: NIH, 2016)
In the first step, the research team isolated T-cells – main target of HIV virus – from donated human blood, hundreds of genes were turned off using CRISPR/Cas9.
Then, the cells that were ‚knocked-out‘ were infected with HIV and analyzed.
- Decreased infection was shown in cells that lost a gene important for viral replication, whereas cells that lost an antiviral factor showed an incresae in infection
- Nearly half of the identified genes were previously discovered, while over half – 46 genes – of the genes hadn’t been looked at before in the context of HIV infection
By further developing this technology, the team wants to enable genome-wide screening where genes are independently turned on or off to indentify all potential HIV host factors.
This data would bring them closer to curative strategies.
Infographic how it could be used for other diseases:
Article 3: Air pollution responsible for 180,000 excess deaths in tropical cities
SD-Date: 8th April, 2022
Et-Date: 10th April, 2022
ScienceDaily Summary: „Around 180,000 avoidable deaths over 14 years in fast-growing tropical cities were caused by a rapid rise in emerging air pollution, a study has revealed.“
Method of Research
For this study, space-based observations from instruments onboard NASA and European Space Agency (ESA) satellites between 2005 to 2018 had been used.
The following cities were analysed in this study:
Africa: Abidjan, Abuja, Addis Ababa, Antananarivo, Bamako, Blantyre, Conakry, Dakar, Dar es Salaam, Ibadan, Kaduna, Kampala, Kano, Khartoum, Kigali, Kinshasa, Lagos, Lilongwe, Luanda, Lubumbashi, Lusaka, Mombasa, N’Djamena, Nairobi, Niamey, Ouagadougou.
South Asia: Ahmedabad, Bangalore, Chennai, Chittagong, Dhaka, Hyderabad, Karachi, Kolkata, Mumbai, Pune, Surat.
Southeast Asia: Bangkok, Hanoi, Ho Chi Minh City, Jakarta, Manila, Phnom Penh, Yangon.
Middle East: Riyadh, Sana’a
- Significant annual increase of pollution directly hazardous to health across all cities:
Up to 14% for nitrogen dioxide (NO2) and for fine articles up to 8% (PM2.5)
- Increases of ‚precursors‘ of PM2.5:
Up to 12% for ammonia and up to 11% for ‚reactive volatile organic compounds‘
- In urban population, the exposure to air pollution increased 1.5- to 4-fold:
NO2: 40 of the 46 cities
PM2.5: 33 of the 46 cities
- Highest number of people dying prematurely due to air pollution:
South Asia, especially Dhaka, Bangladesh (totalling 24,000 people), and the Indian cities of Mumbai, Bangalore, Kolkata, Hyderabad, Chennai, Surat, Pune and Ahmedabad (totalling 100,000 people)
The degradation in air quality was attributed to emerging industries and residential sources like road traffic, waste burning, and widespread use of charcoal and fuelwood.
In tropical cities in Africa, the number of deaths are currently lower „due to recent improvements in healthcare across the continent resulting in a decline in overall premature mortality“, however, it is likely that the worst effects will occur in the decades that follow.
To end it with a quote of Dr Eloise Marais (UCL Geography), a co-author of the study:
„We continue to shift air pollution from one region to the next, rather than learning from errors of the past and ensuring rapid industrialisation and economic development don’t harm public health. We hope our results will incentivise preventative action in the tropics.“