SciCheck Digests Archive

CO2 makes up a small fraction of the gases in the atmosphere, but is very powerful

About 99% of the Earth’s atmosphere is made of just two gases: oxygen and nitrogen. By comparison, the amount of carbon dioxide — which at more than 400 parts per million, is the highest it’s been in several million years — may seem small. It’s equivalent to just 0.04% of the atmosphere.

This fact is often cited by people who are trying to falsely claim that CO2 isn’t responsible for global warming. These individuals also often add that the amount of CO2 from humans is just a fraction of that already small total.

How can carbon dioxide be harmful if it’s ‘plant food’?

The notion that carbon dioxide is “plant food” and that climate change is therefore a good thing or not a problem is a common refrain from those who deny the reality of climate change or who oppose reducing greenhouse emissions.

It’s true that carbon dioxide, the main heat-trapping gas that is causing global warming, is essential for plant growth. Most — but not all plants — tend to respond to increased levels of CO2 by growing more.

But more CO2 is not always good.

How do scientists know climate change is happening?

Multiple lines of evidence, including measurements of a variety of planetary indicators, show that climate change is happening and is caused primarily by human activity. As the concentration of carbon dioxide and other heat-trapping gases in the atmosphere has increased — much of it from burning fossil fuels — land and ocean temperatures have risen, along with sea levels, while sea and land ice have declined.

The changes are consistent with the basic physics of the greenhouse effect that have been understood since the mid-1800s and map to what is expected from human activity.

How is mRNA in vaccines delivered to cells?

Messenger RNA, or mRNA, vaccines work by instructing a small number of a person’s cells to make specific proteins. In the case of the approved mRNA vaccines for COVID-19, the cells make spike protein — one component of the virus that causes COVID-19.

For mRNA vaccines to work, it’s not enough to just put mRNA molecules into a vial and then inject them into a person’s muscle. One innovation that made the current mRNA vaccines possible was the use of lipids to encircle the mRNA molecules.

What ingredients are in vaccines?

All vaccines contain an active ingredient, or antigen, and tiny amounts of other substances that allow them to work, stay free of contamination and remain effective for longer.

The antigen is a substance that prompts the body to mount an immune response, including protective antibodies. Antigens can be viruses, bacteria, parts of those or even the genetic code to produce parts of them. All viruses, bacteria or toxins used in vaccines are either inactivated or weakened so that they can’t make people sick.

What tests are available for COVID-19?

Tests that detect current infections with SARS-CoV-2, the virus that causes COVID-19, are known as viral tests. There are two types: a Nucleic Acid Amplification Test, or NAAT, and an antigen test.
Many of the NAATs use a molecular biology technique known as the polymerase chain reaction, or PCR, to detect even a very tiny amount of the virus in a specimen.
The PCR test takes advantage of some natural features of biology to essentially scan through all of the RNA present in a sample — such as a nasal swab — and search for the presence of coronavirus RNA.

How is COVID-19 transmitted?

SARS-CoV-2, the virus that causes COVID-19, is spread from person to person through respiratory droplets or particles when infected people cough, sneeze, talk or breathe.
Most often, transmission occurs when such droplets or particles are breathed in or land in or on a person’s eyes, nose or mouth. As a result, risk is thought to be highest when people are in close contact with one another, typically within 6 feet or so of an infected person,

What do we know about the origins of SARS-CoV-2?

The exact origin of SARS-CoV-2, the virus that causes the disease COVID-19, remains unknown. Many scientists think that the virus likely originated in bats and then jumped to humans either directly or indirectly, through contact with an animal. Such zoonotic transfers have happened before with the coronaviruses responsible for SARS and MERS.

A paper published in Science in July 2022 analyzed the available evidence and implicated the wildlife trade and the Huanan Seafood Wholesale Market in Wuhan,

What treatments are available for COVID-19?

There are no cures for COVID-19, but an increasing number of evidence-based treatments have been identified. Some of these have emergency use authorization, rather than full approval, from the Food and Drug Administration.
At the end of December 2021, the FDA authorized for emergency use the first oral antivirals for COVID-19, Pfizer’s Paxlovid and Merck’s molnupiravir. Both drugs are authorized for patients with mild-to-moderate COVID-19 who are at high risk of severe disease.

What evidence supports the use of face masks against the coronavirus?

Multiple lines of evidence back the use of face masks to protect against the coronavirus, although some uncertainty remains as to how effective mask interventions are in preventing spread in the community.
Lab tests, for example, show that certain masks and N95 respirators can partially block exhaled respiratory droplets or aerosols, which are thought to be the primary ways the virus spreads.
Observational studies, while limited, have generally found mask-wearing to be associated with a reduced risk of contracting the virus or fewer COVID-19 cases in a community.