Just how bad is it?

Cliff Mitchell - 28/12/2019

How high could temperatures go?

You understand climate change but want to know more about just how bad it is.

Because of the greenhouse gases we have been pumping into the atmosphere global average temperatures have increased by 1.1°C since the pre-industrial period. This may not sound much but a one-degree global change is actually massive because it takes a vast amount of heat to warm all the oceans, atmosphere, and land by that much. In the past, a one- to two-degree drop was all it took to plunge the Earth into the Little Ice Age.

Heat is a form of energy so global warming is actually putting huge amounts of additional energy into the earth’s ecosystem. That additional energy has huge effects on every aspect of life on earth including rising sea levels, regional changes in precipitation, more frequent extreme weather events such as heat waves, and expansion of deserts. Ocean acidification is also caused by greenhouse gas emissions and is commonly grouped with these effects even though it is not driven by temperature. Surface temperature increases are greatest in the Arctic, which has contributed to the retreat of glaciers, permafrost, and sea ice. Overall, higher temperatures bring more rain and snowfall, but for some regions droughts and wildfires increase instead. Climate change threatens to diminish crop yields, harming food security, and rising sea levels may flood coastal infrastructure and force the abandonment of many coastal cities. Environmental impacts include the extinction or relocation of many species as their ecosystems change, most immediately the environments of coral reefs, mountains, and the Arctic.

How much CO2 are we putting into our atmosphere?

Global annual mean carbon dioxide (CO2) concentration has increased by more than 45% since the start of the Industrial Revolution, from 280 ppm (ppm = parts per million) during the 10,000 years up to the mid-18th century to 415 ppm as of May 2019. The present concentration is the highest for 14 million years.

Each part per million by volume of CO2 in the atmosphere represents approximately 2.13 gigatonnes of carbon, or 7.82 gigatonnes of CO2.

A gigatonne is 1,000,000,000 tonnes. Just think about that. We have put an additional 135 (i.e. 415 ppm minus 280 ppm) ppm of CO2 gas into our atmosphere since the mid-18th century. That means we have pumpled 7.82 x 135 = 1,055,700,000,000 tonnes of CO2 gas into our atmosphere - and we wonder why our climate is changing!

The global mean CO2 concentration is currently rising at a rate of approximately 2 ppm/year and accelerating.

Won't it soon go away naturally?

If we somehow managed to stop emiting CO2  into the atmosphere wouldn't global warming stop straight away? Sadly, no! Researchers have estimated that about 50 percent of the CO2  we have pumped into the atmosphere would be absorbed in the first 50 years, and about 70 percent in the first 100 years. But after that things slow down considerably, with an additional 10 percent or so being removed after 300 years and the remaining 20 percent lasting tens if not hundreds of thousands of years before being removed.

So while a good portion of warming attributable to carbon and other greenhouse gas emissions would be removed from the atmosphere in a few decades if emissions were somehow ceased immediately, about 10 percent will continue warming Earth for eons to come. This 10 percent is significant, because even a small increase in atmospheric greenhouse gases can have a large impact on things like ice sheets and sea level if it persists over the millennia.

How hot could it get?

If we carry on as we are, global warming is expected to reach 4.1°C – 4.8°C above pre-industrial by the end of this century. The emissions that drive this warming are often called Baseline scenarios because they represent what will happend if we continue without any new policies to address climate change. Current policies presently in place around the world are projected to reduce baseline emissions and result in about 3.0°C warming above pre-industrial levels. The unconditional pledges and targets that governments have made, as of December 2019, would limit warming to about 2.8°C above pre-industrial levels.

There remains a substantial gap between what governments have promised to do and the total level of actions they have undertaken to date.

Limiting warming to 1.5°C above pre-industrial levels, regarded as the mxiumum increase that would avoid disastrous climate change, by 2100 means that the emissions of greenhouse gases need to be reduced rapidly in the coming years and decades, and brought to zero around mid-century.

Does it matter?

Human activity is causing irreparable harm to life on earth.

Many current life forms will be extinct by the end of this century. We may right now be causing the Sixth Mass Extinction in Earth’s history.

The air we breathe, the water we drink, the earth we plant in, the food we eat, and the beauty and diversity of nature that nourishes our psychological well-being – our very health – all are being corrupted and compromised by the human values behind our political and economic systems and consumer-focussed lifestyles.

The effects of climate and ecological disruption that we are experiencing now are nothing compared to what could come.  Catastrophic effects on human society and the natural world may spiral out of control if this climate and ecological emergency is not addressed in time.

  • Biodiversity Loss
  • Sea level rise
  • Desertification
  • Wildfires
  • Water shortage
  • Crop failure
  • Extreme weather

The combined result of these destabilising events will be:

  • Millions displaced
  • Disease
  • Increased risk of wars and conflicts
  • Impacts on human rights

Mass Extinctions

More than a quarter of approximately 100,000 species assessed by the IUCN are threatened with extinction; 40% of all amphibians, 25% of all mammals, 34% of all conifers, 14% of all birds, 33% of reef-building corals, 31% of sharks and rays. IPBES estimated that a million species of animal and plant are already threatened with extinction because of human action.


Overall, climate change is already having severe impacts and making extreme weather more likely across the world. World Meteorological Organization data shows that there has been a dramatic increase in the number of extreme weather disasters around the globe. (Mass movement wet is defined as subsidences, rockfalls, avalanches and landslides.)

The science is clear: It is understood that we are facing an unprecedented global emergency. We are in a life or death situation of our own making. We must act now.

We face a direct existential threat…Our fate is in our hands.”-  António Guterres (UN Secretary-General).

If we do not change course by the end of the 2020s, we risk missing the point where we can avoid uncontrollable climate and ecological breakdown, with disastrous consequences for people and for all life on Earth.

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Cliff Mitchell
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