Scientists are, by their very nature, a cautious lot – determined not to jump to conclusions. That’s why yesterday’s report from the Intergovernmental Panel on Climate Change (IPCC) is salted with phrases outlining just how sure the authors think they are on their predictions.

That the glaciers continue to shrink worldwide is rated with “high confidence”, while the negative impact of climate change on wheat and maize yields is stated with “medium confidence”. There are comparatively few statements in the report held in “low confidence”, partly because such predictions would hardly merit inclusion, but also because – one suspects the authors are trying to say – the evidence is now so overwhelming we can be more than reasonably confident on most points.

Yesterday’s Working Group II report (the final version will be presented in October) draws on a vast quantity of new research published since the last major IPCC survey in 2007. It is the product of 436 contributing authors, cites 12,000 scientific references, and has been looked at by 1,729 expert reviewers from 84 countries.

One of its many areas of study is that of food security and production. It states that production of major crops in tropical and temperate regions will be negatively impacted by temperature rises of 2°C, with some regions facing yield losses of more than 25%: “Climate change is projected to progressively increase inter-annual variability of crop yields in many regions. These projected impacts will occur in the context of rapidly rising crop demand.”

All aspects of food security will potentially be affected by climate change, the document continues, from access to price stability: “Global temperature increases of ~4°C or more above late-20th-century levels [the more extreme of two scenarios modelled], combined with increasing food demand, would pose large risks to food security globally and regionally.” A breakdown of food systems would most likely hit poorer, rural populations hardest, the report adds.

If the findings are alarming, the authors are at least trying to avoid being alarmist. There is a marked attempt to discuss “adaptation” to climate change’s effects, rather than solely mitigation – which could be seen as either throwing in the towel or making a stark adjustment to reality, depending on your point of view.

“It’s a real difference in messaging from the IPCC to put a lot more emphasis on the new science that says what we can accomplish with ambitious investments in both mitigation and adaptation,” Dr Chris Field, co-chair of the working group, told the BBC yesterday – though he still insisted the world would need to see an “aggressive decrease” in carbon emissions.

This emphasis on “adaptation” still did not go far enough for one of the report’s authors, Richard Tol, who took his name off the final work and garnered plenty of publicity in the process. Farmers “are not stupid”, Tol said, adding that they would adapt their crops to changing climate: “It is pretty damn obvious that there are positive impacts of climate change, even though we are not always allowed to talk about them.”

In fact the report does strain to identify some silver linings: “Positive effects are expected to include modest reductions in cold-related mortality and morbidity in some areas due to fewer cold extremes” (interestingly, this is one of the few predictions made with “low confidence”). The IPCC also foresees geographic shifts in food production, with some areas potentially seeing an increase in crop yields.

But the overall report makes for very sobering reading, even with the cautious scientific language used. “We live in an era of man-made climate change,” said Vicente Barros, co-chair. “In many cases, we are not prepared for the climate-related risks that we already face. Investments in better preparation can pay dividends both for the present and for the future.”

Will this change of tack to emphasise adaptation and investment spur greater action on climate change? For all the damning evidence presented in the study, and the sheer number of scientists that have contributed, it’s hard to have “high confidence” that it will.

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