The Intergovernmental Panel on Climate Change does not have a political agenda, nor does it recommend any particular course of action. Its mandate is to provide scientifically robust, reliable information to guide decision-makers – and it does so with great care and deliberation.

The first part of the IPCC’s Fifth Assessment Report, released on 27 September in Stockholm, was produced by 259 scientists and reviewed by more than 1,000 outsiders. “I know of no report that has been scrutinized so carefully”, said Thomas Stocker, co-chair of IPCC Working Group I.

This is important to remember when reading the stark messages in the Summary for Policymakers:

• Warming of the climate system is “unequivocal”, and many of the observed changes since the 1950s are “unprecedented over decades to millennia”.

• It is “extremely likely” that human influence “has been the dominant cause” of that warming, and human influence has also been detected in changes in the global water cycle, reductions in snow and ice, global mean sea level rise, and changes in some climate extremes.

• By 2100, global surface warming compared with 1850-1900 is “likely” to exceed 1.5°C, except under a mitigation scenario more ambitious than ever before envisioned in an IPCC report. It is also “more likely than not” to exceed 2°C under a scenario akin to what we used to consider ambitious.

None of this is a surprise. The IPCC only reviews published studies; the scientific evidence has been building up for years – as have the news reports. Yet action on climate change has been slow, hindered to a great extent by fear that it would harm the economy.

Yet the new IPCC report shows the price of waiting. The only scenario that avoids a more than 50% chance of exceeding 2°C of warming is RCP 2.6, which requires emissions to peak by 2020, and decline to “negative” emissions by 2100. Under business as usual (RCP 8.5), warming is “about as likely as not” to exceed 4°C – a dangerous future that the World Bank warns “must be avoided”.

“Business as usual” does not apply just to public policy. It is, in fact, primarily about business – about the global economy, what we buy and sell, what resources we exploit, what we invest in (or not). Every good and service has a carbon footprint, and all those footprints add up.

Consumer demand for “greener” products is driving businesses to take action, but not fast enough. Yet as companies from Apple to IKEA have shown, success requires not just responding to demand, but creating it. Some are already driving demand for sustainable goods and services; we need more.

Businesses also need to focus less on short-term gains, which are often pursued at the expense of long-term investments in resource efficiency and overall sustainability. We know this is difficult in the face of investor and shareholder pressure, but some companies have proven it can be done.

Lastly, but importantly, businesses need to understand their own exposure to climate risks. In a global economy, climate impacts can have repercussions thousands of kilometres away. Every company needs to examine its supply chains and operations, identify the risks, and address them.

A key message in the IPCC report is that we have a choice. We know the science, and the huge difference between low- and high-emission pathways. What happens next is in our hands.