Is the earth actually getting hotter or colder? And who’s really responsible – is it mankind or is it the sun? These are some of the key points to be debated at an international conference in Israel starting today and running until Thursday, April 29.

Experts from Israel, India, Canada, Germany, Denmark, Finland, Britain and Switzerland are meeting at the Hebrew University (HU) of Jerusalem for the ‘Solar, Cosmic Rays and Climate Connections’ conference.

According to one of the conference organizers, Prof. Nir Shaviv of the Racah Institute of Physics at HU, the key issue to be debated will be the relative climatic role played by the sun.

“… If the sun is an important climate driver, some of the 20th century warming should be attributed to the sun – implying that the human role is smaller and with it the expected warming over the 21st century,” says Shaviv.

However, other experts – among them, Prof. Juerg Beer of the EAWAG Research Institute in Switzerland – claim that global warming is influenced more by the actions of mankind. According to this hypothesis, the warming of the earth will continue in the 21st century at a rate of up to 0.2 degrees per decade.