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Adelle Rodda breaks down the science of climate change

Climate scientists have been stuck on repeat like broken records for years now: the climate is changing, humans are mostly to blame and, in order to avoid some pretty catastrophic consequences, we must reduce global greenhouse gas emissions and end our dependency on fossil fuels.

The current international – though not legally binding – agreement, the Copenhagen Accord, requires that global temperatures do not exceed 2°C above what they were in pre-industrial times. If warming goes beyond this limit, we’re pretty much screwed. Earth’s thermometer currently reads 0.9°C higher than at the dawn of the Industrial Revolution 130 years ago, and with the rate of warming increasing each century we look set to pass the 2°C threshold by 2050 and reach at least 4°C by the end of this century – unless we seriously get our acts together.

Already, the effects of a warmer climate have begun to materialise. Sea and land ice is disappearing at an alarming rate, oceans are rising and extreme weather events are escalating in both frequency and severity. The aforementioned are a mere taste of things to come if the Intergovernmental Panel on Climate Change (IPCC) projections are anything to go by, and they are. Established in 1988 by the UN and World Meteorological Organization, the panel is the global authority on climate change science.

According to the most recent report released by the IPCC, if we continue our current trend of unabated – business as usual – greenhouse gas emissions, we can expect a number of consequences, including, but not limited to:

A rise in global sea levels of up to 1 m by the end of this century
Entire island nations will be lost to the ocean, and hundreds of millions of people living in coastal areas and low-lying regions will be displaced. As sea levels rise, so too does the risk of storm surges, flooding and erosion putting millions of lives at risk and causing untold billions of dollars worth of damage to coastal property and infrastructure.

Water scarcity
Renewable surface and ground water supplies will be significantly reduced in most dry subtropical regions, and with each degree of warming hundreds of millions of people worldwide will lose at least one-fifth of their water resources.

Ice-free summers in the Arctic Ocean by as early as 2050
Polar bears will become extinct and, as well as adding to the ocean’s volume and causing sea levels to rise further, the loss of ice will be in effect like losing a giant sun reflector – escalating surface warming further.

Extinctions and decreased biodiversity
Freshwater and terrestrial ecosystems will suffer irreversible changes to their structure, function and composition. Forest dieback will occur across many regions – releasing more carbon dioxide (CO2) into the atmosphere – and a substantial number of species, unable to adapt fast enough, will face extinction by the end of this century.

Warmer, more acidic oceans
Rising seawater temperatures will affect ocean circulation, resulting in habitat shifts, population declines and local extinctions of many marine species; low latitude regions will also experience significant decreases in fisheries catch. As oceans continue to acidify – a result of absorbing CO2 from the atmosphere – marine life will suffer dire consequences, especially organisms with carbonate shells and coral reefs, which support diverse ecosystems and the livelihoods of some 500 million people.

Extreme weather
Already wet regions will experience wetter and more prolonged rainy seasons; conversely, dry areas will experience longer, more severe periods of drought. The occurrence of record-breaking hot months, which are happening five times more frequently now than when the climate was stable, will also continue to increase as global temperatures do.

Food security issues
Freshwater scarcity and changes in weather patterns will have mostly negative impacts on agriculture and livestock. Some crops may experience yield losses of 25% or more in the first half of this century alone – major crops like wheat, corn and rice are particularly susceptible. Food security will be affected both regionally and globally, and unsurprisingly, those in developing countries already struggling with hunger and malnutrition will experience the worst shortages.

Injury, disease and mortality rates from heatwaves and wildfires will rise. Climate change will exacerbate malnutrition, starvation and existing health problems – especially in poorer regions – and the prevalence of water-borne, food-borne and vector-transmitted illnesses like malaria will increase and spread.

Climate change impacts are expected to slow economic growth this century, affecting livelihoods through loss of work and food price increases etc., creating new pockets of poverty – particularly in urban areas – and amplifying already poverty-stricken zones. Water and food shortages, the displacement of hundreds of millions of people because of sea level rise and extreme weather, along with numerous other climate-related drivers will create competition amongst sectors, regions and even nations for resources – resulting in conflicts, violence and war.

Suffice it to say, there are a lot of terrifying things for the human race to look forward to later this century if we do nothing to curb our emissions. It’s not all bad news though – some of the scenarios outlined above can be avoided and others can be minimised, IF we can keep warming below the target set at the Copenhagen Accord. In order to do this, it must be acknowledged that there is a finite amount of CO2 – a “global carbon budget” – that can be emitted to keep warming below 2°C relative to the pre-industrial era. Unfortunately, by 2011 we had already spent two-thirds of this budget, and at this rate will have burnt through the remaining 270 billion tonne allowance in about 25 years, begging the question: are we already too late?

Perhaps not. There is no magic bullet – it will take some drastic measures, sacrifices and behavioural changes on our part – but it can be done. According to the IPCC, to avoid the worst-case scenario we need to cut emissions by at least 40-70% by 2050, and reach zero emissions by 2100.

This can be achieved through a combination of pathways, including: substantially increasing the amount of energy sourced from renewables; the use of carbon capture and storage (CCS) and carbon dioxide removal (CDR) technologies; changing the way we use land (e.g. reforestation instead of deforestation); and most importantly, leaving the remaining fossil fuel reserves buried in the ground. The latter will no doubt prove to be the most difficult hurdle to overcome – the arduous, near-impossible task of persuading energy companies to leave untapped ‘black gold’ alone. No government has ever before forsaken the economic gains of fossil fuel extraction for the wellbeing of the planet – but there is a first time for everything, and that time is now.

It is up to civilisation today to choose the kind of world future generations will live in. Unfortunately, any scenario will take some adaptation, as we have already set off an unstoppable chain of events, but the action or inaction we take now will determine how bad things get and the kind of legacy we leave behind. Human intelligence and technology helped put us in this mess and they are the very things we’ll need to help get us out. On a positive note, carbon capture, storage and removal technologies are already being utilised, with improvements and new methods being constantly researched and developed. Alternative energy sources are becoming more widely adopted and grassroots movements are springing up across the globe.

Mankind has achieved incredible feats. We have split the atom and walked on the moon. We can – at least in theory – also find a way to end our relationship with fossil fuels.

Adelle Rodda is a science writer and (excellent) hairstylist. Read more by Adelle.