"Widespread" and "unprecedented" changes are already upon us.

Like Pandora's gift from Zeus, the gift of fossil fuels has come with some very unexpected — and unfortunately very nasty — downsides.

Fortunately, we now have the unprecedented power of modern science to inform us about the miseries that are escaping. Will humanity heed these warnings and close the lid in time?

To give a brief flavour of what the latest and best climate science is telling us, I compiled key quotes and highlights from the world's most respected source: the International Panel on Climate Change (IPCC) Fifth Assessment report.

This is the report that all the nations attending the Paris 2015 UN climate change conference will be relying upon to understand the climate risks and options. I've grouped quotes and highlights from the report by theme and added some emphasis.

Climate change is happening right now

The IPCC report clearly states that climate change is taking place today. Here are some quotes:

"Warming of the climate system is unequivocal."

"Changes in many extreme weather and climate events have been observed since about 1950."

"Many of the observed changes are unprecedented over decades to millennia."

"Recent climate changes have had widespread impacts on human and natural systems … [including] changes in many extreme weather and climate events."

Impacts will last for centuries

"Most aspects of climate change will persist for many centuries even if emissions of CO2 are stopped. This represents a substantial multi-century climate change commitment," the report also states.

Current course: > 4oC

"Without additional mitigation efforts beyond those in place today, and even with adaptation, warming by the end of the century will…"

  • "more likely than not exceed 4°C" and could reach 7.8°C
  • cause "high to very high risk of severe, widespread, and irreversible impacts globally."
  • cause "substantial species extinction, global and regional food insecurity, consequential constraints on common human activities … including growing food and working outdoors … and limited potential for adaptation in some cases."

The expanding parade of misery

"Continued emission of greenhouse gases will cause further warming and long-lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems," including:

  • worsening ocean acidification (seas are 26 per cent more acidic already over the baseline levels)
  • rising sea levels
  • more damaging storm surges
  • more and longer heat waves
  • more extreme hot temperatures
  • increasing droughts
  • emerging hunger hotspots
  • increasing displacement of people and violent conflicts
  • increasing wildfires
  • shifting atmospheric circulation including changes to jet stream locations and strength
  • increasing and substantial extinction of species
  • more intense and more frequent extreme rainfall events
  • increased landslides
  • shifting monsoon seasons and intensity
  • changing global water cycle with a pattern of wet regions getting ever wetter and dry regions drying out ever more
  • greater flooding in some regions
  • increasing melt of permafrost and the release of GHGs
  • increasing air pollution in some areas
  • expanding range for many diseases and parasites
  • decreasing yield of major crops creating large risks to food security globally
  • warmer oceans with more extreme wave heights
  • increase in most powerful cyclones and hurricanes
  • decreasing oxygen levels in oceans
  • shifts in major ocean currents
  • melting of Greenland and Antarctic ice sheets
  • increasing die-off of coral reefs
  • reduction in water supplies through decreasing snow cover and glaciers

Some of the big unknowns

"The precise levels of climate change sufficient to trigger abrupt and irreversible change remain uncertain, but the risk associated with crossing such thresholds increases with rising temperature," the report warns. The best science is unable to rule out such rapid and calamitous earth-system tipping points as:

  • the die-back of the Amazon rainforest
  • dramatic changes to the global oreal forest
  • collapse of a critical Atlantic current under biz-as-usual emissions
  • abrupt change in ice sheet outflows leading to more rapid sea level rise. (For example: former NASA climate scientist, Dr James Hansen, says up to 5 meters (16 feet) of sea level rise is possible this century.)1
  • abrupt increase in extreme weather events caused by jet stream getting "stuck" more often. (For example: Dr. Jennifer Francis says the jet stream is already getting "blocked" more often as a result of the collapse of the Arctic sea ice, which is leading to more persistent droughts, deluges and blizzards.")2

Safe climate requires a cumulative carbon budget

"Cumulative emissions of CO2 largely determine global mean surface warming"

"Emissions scenarios … likely to maintain warming below 2°C… are characterized by":

  • "cumulative CO2 budget from 2011 to 2100" of ~900 GtCO2"
  • "40 per cent to 70 per cent emissions reductions by 2050"
  • emissions "reductions of 90 per cent or more between 2040 and 2070"
  • "emissions levels near zero or below in 2100"

Solutions inexpensive if action taken soon

"We have the means to limit climate change and build a more prosperous, sustainable future."

The IPCC report says that multiple economic models suggest that keeping climate change below 2°C could be done with as little as a one per cent loss in cumulative economic growth.

For example, the average of the economic models the IPCC evaluated found that the costs to keep global warming below 2°C would reduce economic growth over the next century from 600 per cent down to 595 per cent. To keep costs down however requires using the most economically-efficient climate policies, such as an economy-wide price on carbon.

Delay = more coal now, less oil in the future

Delays in mitigation "lead to higher utilization of… coal in particular, in the short run… To compensate… particularly oil and gas would need to be reduced much more strongly in the long run."

Notes and sources

Every few years the United Nations IPCC compiles the latest climate science from more than 30,000 peer-reviewed studies by over 800 climate scientists in 80 different nations. Then every major nation — including the federal governments of the biggest climate polluting nations of China, USA, India, Russia, Japan, Germany, South Korea, Saudi Arabia, Canada, Brazil, and the UK — approve, line by line, the summary and basic findings. The most recent IPCC report (Fifth Assessment) was released in 2014.

Its four volumes contain thousands of pages covering nearly every aspect of climate research. It is the most authoritative and respected summary of the science and is used by the world's major governments, businesses and civil society to understand and take action on the climate threat.


1 Hansen paper: Greenland Ice Sheet Update (pdf)

2 The Economist's article on polar warming to blame for America's and Britain's bad winter weather discusses Dr. Francis theory. IPCC 2014 AR5 says "trends in blocking intensity and persistence remain uncertain".

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