'You're right, People dying thanks to climate change is a long way off. About 5,000 miles, give or take'. That's the message greeting tens of thousands passengers using London's tube system each day as one international development charity steps up against its fight against the public's apathy to the effects of climate change.

Such a tactic is far from unique. Indeed, when it comes to climate change, charities, campaigning groups and NGOs are increasingly making use of apocalyptic rhetoric to highlight the immediacy of the threat facing humanity. At the same time, doomsday scenarios revolving around rising tides or dramatic weather changes are now entertainment, with everything from blockbuster movies forecasting the dawn of a new ice age to coffee table books showing what major cities will look like underwater striking a popular chord with the public.

However, according to a new report published by scientists working at the University of California, Berkeley, far from urging people to take action, such bleak and emotionally-charged warnings over the potential consequences of global warming may have the opposite effect, prompting not only ongoing lethargy but also denial.

"Fear-based appeals, especially when not coupled with a clear solution, can backfire and undermine the intended effects of a message," the report warns.

The scientists reached this conclusion after conducting a pair of linked experiments aimed at analysing attitudes to global warming and the concept of fairness in the world. In the first experiment, a group of UC Berkeley undergraduates were asked to state to what degree they agree that the world is either just or unjust, both for themselves and for others. The study participants were then asked to read two distinct versions of a single news article about global warming.

While both versions of the story made use of factual data provided by the United Nations Intergovernmental Panel on Climate Change, one concluded with a positive message highlighting the potential solutions to the problem of global warming, while the other painted a 'doomsday scenario'. Notably, those participants who read the more-upbeat version of the story tended to express a greater level of optimism in science's ability to tackle the threat of climate change, particularly if they also expressed a strong belief in a 'just world'.

At the same time, however, those participants who were presented with the pessimistic version of the news story were found to be more skeptical over the threat of global warming, with this also seen to be more marked among those who expressed a strong belief that the world is just.

In a separate study, the California-based researchers primed a group of 45 online participants to watch a video of innocent children under threat from the potential consequences of global warming, having already been primed to assume a view of the world being just through unscrambling a number of optimistic sentences such as "prevails justice always".

Again, the team found that this combination of believing that, by and large, people get what they deserve, and a doomsday view of the effects of global warming tended to boost skepticism about climate change, with a majority of the online participants expressing little or no willingness to adjust their lifestyles so as to minimise the size of their carbon footprints once the test was over.

Writing up the findings for a forthcoming issue of the journal Psychological Science, Matthew Feinberg, who co-authored the study, concluded: "The scarier the message, the more people who are committed to viewing the world as fundamentally stable and fair are motivated to deny it."

The report suggests, therefore, that, though shock tactics may well grab the public's attention, charities and NGOs need to tread the fine line between jolting people into taking action yet at the same time downgrading any sense of futility, a tough task indeed given the sheer number and range of causes vying for attention on the walls of the London Underground and other public spaces around the world.