SIPTU General Secretary, Joe O'Flynn said he was happy to offer the Union's support to the Earth Hour 2008 global campaign.
"Just as trade unions in developed and developing nations understand the strength of collective action, we also understand the need to tackle the threat of global warming," he said.
"We believe that the challenge of climate change requires extraordinary steps to be taken to engage with people at all levels in the campaign if we are to raise awareness to the threats posed.
"It is not enough to lobby and persuade governments. The engagement of millions of ordinary people is required and unions are a vital link in that process of mobilisation.
"SIPTU will lend its support by not only raising awareness amongst our Union members but also by ensuring that Liberty Hall - one of Dublin's iconic landmarks switches off on March 29 from 8-9 pm, he concluded.