Every few years, thousands of the world's most renowned climate scientists work together as part of the Intergovernmental Panel on Climate Change (IPCC) to present us with the latest scientific assessment of how we are doing in terms of protecting the planet for future generations. This week they are finalising their latest assessment on climate change impacts in Japan.

And – you might have already guessed – we're not doing too great at the moment. In fact, the science is now clearer than ever: if we want to have a realistic chance at stopping climate change we not only need to phase out fossil fuels but we have to protect the world's remaining forests.

The reason for this is quite simple: deforestation, together with climate change, makes for a vicious cocktail. Why is this? The science shows that climate change is likely to lead to more intense periods of droughts in some tropical rainforests, increasing their vulnerability to fire. Add deforestation to that and you have a recipe for disaster. Deforestation fragments the remaining forest, making it even more vulnerable to drought-induced fires. Forest fires then release carbon, triggering even more climate change. Last year's massive forest fires in Indonesia were a stark reminder of what that future might look like if we do not end deforestation by the end of this decade.

Documenting Forest Fires in Sumatra. 06/23/2013 © Ulet Ifansasti / Greenpeace

This vicious cocktail becomes even more of a problem for the world's largest remaining rainforest, the Amazon. Here there is a risk that it could lead to a "tipping point" with disastrous consequences. The combination of climate change and deforestation could cause the forest to rapidly change into savannah, thereby losing much of its biodiversity and at the same time releasing carbon. However, this does not have to happen. Scientists today also leave us with a bit of hope (or, one could say, a big warning sign): as worrying as this tipping point is, we stand a realistic chance to avoid this from happening if we manage to keep the rise in temperatures below 2°C and prevent fragmentation of the Amazon. Keeping tropical forests as intact, unfragmented landscapes allows them to maintain their resilience to climate change. Therefore, alongside phasing out fossil fuel emissions, we need to cut deforestation rates and conserve the intactness of tropical forests so they remain the breath-taking wilderness we know today.

The new evidence the IPCC is expected to include in their assessment not only describes the expected impacts climate change will have on forests but also highlights what we are already witnessing. A changing climate puts additional pressure on forests and their ecosystems. Climate change and forest fires have not just threatened the rainforests of Indonesia and the Amazon in recent years. The heat wave in Russia in 2010 alone caused more than 1 million hectares of boreal forests to burn down. According to the World Bank such extreme weather events and their dramatic consequences for the world's forests could become the new normal if we don't stop climate change.

Forest Fires in Russia. 08/11/2010 © Greenpeace / Igor Podgorny

To put things in perspective, deforestation globally accounts for about 12% of total man-made greenhouse gas (GHG) emissions. In other words deforestation causes roughly as many emissions as all the world's cars, planes, ships and trains taken together. So forests are a big deal. But forests do much more than just cause GHG emissions: they also soak up a portion of humankind's greenhouse gases. That means that deforestation delivers a double whammy – forest destruction releases emissions into the atmosphere (mostly carbon dioxide) whilst at the same time reducing the forests' ability to soak up greenhouse gases and thereby limit climate change.

However, the story does not end here. While forest protection is important in bringing down emissions and mitigating climate change, forests also play a crucial role in allowing the world to adapt to the consequences of climate change that are already inevitable. We need forests because they provide many essential ‘services', such as food and raw materials, or even things like regulating the water flow of rainfalls. We need all of that to be able to adapt to a changing climate. Maintaining forests as intact is one of the most important things we can do to enable the species living within them (hint: we are one of them) to adapt to a changing climate.

The way ahead is obvious. The science has stated the facts loud and clear but it is us who have to act: Only if we succeed in leaving most of the remaining fossil fuels in the ground while at the same time stopping companies like Procter & Gamble from destroying the world's forests and getting governments to commit to Zero Deforestation policies, do we have a chance to save the climate.

Dr. Janet Cotter is a senior scientist at Greenpeace's Science Unit.

Sebastian Bock is a political advisor for forest and climate policies. You can follow him on Twitter @sebastianbock