Some colors that people see late at night could cause signs of the condition mental health experts call clinical depression. That was the finding of a study that builds on earlier study findings. They show that individuals who live or work in low levels of light overnight can develop clinical depression.

Doctors use the words “clinical depression” to describe severe form of depression. Signs may include loss of interest or pleasure in most activities, low energy levels and thoughts of death or suicide.

In the new study, American investigators designed an experiment that exposed hamsters to different colors. The animals were separated into 4 groups. One group of hamsters was kept in the dark during their nighttime period. Another group was placed in blue light, a third group slept in white light. While a fourth was put in red light. After four weeks, the researchers noted how much sugary water the hamsters drank. They found that the more depressed animals drank the less amount of water.

Randy Nelson, who heads the Department of Neuroscience at Ohio State University, says animals that slept in blue and white light appeared to be the most depressed. “What we saw is these animals didn’t show any sleep disruptions at all but they did have messed up circadian clock genes and they did show sign of depression whereas if they were in the pale red light, they did not.” He says there’s a lot of blue in white light, which explains why the blue light and white light hamsters appear to be more depressed than the hamsters that see red light or darkness.

Mr. Nelson has suggestions for people who work late at night, or those who like to stay up late. “My recommendation is if you are just living a typical mostly active life during the day, mostly inactive at night, you need to limit exposure to TVs which are quite bluish in the light they give off and computer screens and things like that. You can get filtered glass, you can get filters on your computer screen and filters on your e-Readers to put it more in the reddish light.”

The world’s weakest countries are said to be preparing to take on the richest countries with a demand for money—possibly including new taxes(税)on oil or flying—for the irrecoverable losses they are suffering from the climate change.

Extreme weather is already hitting many developing countries hard and is expected to cause further catastrophes. Loss and damage—the issue of how to help poor nations suffering from the most extreme effects of climate breakdown, which countries cannot be protected against—is one of the problems that cause disagreement in climate discussions.

Some of the world’s weakest countries have prepared a paper for discussion this week at the UN general meeting in New York. It shows they are preparing to ask for a “climate-related” global tax as a way of funding payments for loss and damage.

The funds could be raised in several ways: by a global carbon(碳)tax; a tax on airline travel; a tax on the heavily polluting oil used by ships; adding taxes to oil production; or a tax on financial business. The discussion paper notes the pros and cons of each of these, and the choices of raising funds through development banks and from the private sector.

Nations will meet again for fresh talks called COP27 in Egypt in November, where loss and damage is expected to be a major topic of discussion. At COP26, the UN climate meeting held in Glasgow in 2021, there was an agreement on the need to limit global temperature rises to 1.5℃ above pre-industrial levels.

Damage to poor countries is set to increase. A separate submission(呈递)to the UN, by Antigua and Barbuda, warns that increasing sea and air temperatures in the Caribbean could create a superstorm within years that would cause $9 billion(£7.8 billion)in damage to the island nation alone, six times its yearly GDP.