Should we paint roofs into white?

Question

How would that fight the mean evergreen forests which do not compensate their existence by taking away the area of white snow?

Answer 1

You may have noticed that in hot countries a lot of the buildings are painted white, the reason being to reflect the sunlight and reduce the warming of the buildings themselves.

White surfaces reflect sunlight, black ones abosrb it with the varying shades of darkness absorbing proportional amounts of sunlight.

Painting roofs white would help to reduce global warming by reflecting solar radiation back into space but the effect would be a small one.

Here's some very rough figures. The UK has 60 million people and 22 million homes - approx 1 home per 3 people, add in shops, offices etc and lets say 1 building for every 2 people. 6.5 billion people on the planet so let's say 3.25 billion buildings, average area covered per building = 50 sqaure metres, total roof area globally = 325,000 square km or roughly 0.5% of the planet's surface. A small amount in the larger scheme of things.

Evergreen forests (or even single trees) planted in locations prone to snow cover can do more harm than good in respect of their contribution to global warming. Snow and ice reflects almost all incoming solar radiation whereas the dark canopy of a forest absorbs solar radiation only to release it later as thermal radiation (when the ambient temp drops). It's the longer wavelength thermal radiation that is trapped by the atmospheric greenhouse gases.

As a very rough guide - one mature broadleaf planted in a tropical zone has a net contribution equivalent to the removal of 40kg of CO2 per year, the same tree but in a snowy environment would produce the equivalent of adding 20kg of CO2 to the atmosphere.

Trees grow slower in cold, cloudy climates so it's financially beneficial to plant commercial forests in warmer areas where they're likely to have a positive impact on the environment. Conversely, much of the 'good' land is taken up by farming so forests are often planted in colder areas due to a lack of alternative land.

Answer 2

In warm climates that would do some good, mostly by enabling people to use less (energy consuming) air conditioning. In cold climates it would do more harm than good, requiring more heating.

The total area of housetops just isn't that large.

Answer 3

not me the sun helps warm my house in winter so I can use less oil to heat my home which helps the enviroment because I burn less oil if I used white I would have to use more oil creating more so called pollution.

RRRR