The actions taken to contain the corona-virus epidemic is closing any form of human activities in the world. Schools are closed in most cities of the world, people are told to stay at home and it seems industries are also partially closed. So, chemical emissions from industries and cars will lower significantly. How does this affect the air quality, weather and climate?
This is a topic of almost continual discussion in the South China Morning Post, scmp.com , an English language newspaper in Hong Kong. This is both because air quality is a major problem in China (but one to which they are paying a good deal of attention) and because massive economic interruptions are relatively frequent. The Olympics were a big one, national festivals like Spring Festival, 春节, Chūn jié, give readers a chance to mourn or hope, the current trade war modulates the scale of industry, and now we have Covid-19.
Obviously the virus crisis is bringing about great improvement in current air quality almost everywhere. I doubt that any climatic effects are known yet.
Here's an article which introduces the topic in China -- which is, after all, the major live experiment going on: https://www.scmp.com/news/china/society/article/3044747/beijings-air-quality-shows-significant-improvements-war
This study suggests that the effect on climate change will be neglible:
Forster et. al. (2020): Current and future global climate impacts resulting from COVID-19
[...] As a result, we estimate that the direct effect of the pandemic-driven response will be negligible, with a cooling of around 0.01 ± 0.005 °C by 2030 compared to a baseline scenario that follows current national policies. [...]
In other words, if there are no changes to the economy, there will be no positive effect on climate change.