4 irrefutable truths about climate change science

During the recent confirmation hearings of President Trump’s Cabinet nominees, a familiar pattern has emerged. Many of them have acknowledged that climate change is happening, but each has sowed doubt by either understating the connection between human activity and climate change or by suggesting that there’s too much uncertainty to act. The overall effect of these statements is to confuse or stall progress.

The reality is that we know plenty about the role of people as primary driverS of climate change, and government officials certainly know more than enough to act.

Well-established science from leading national and international scientific institutions, including Inter-governmental Panel on Climate Change, National Climate Assessment, World Meteorological Organisation, National Academy of Sciences and UK Meteorology Office, shows the connection between increasing CO2 concentrations and a warming planet was established more than 150 years ago.

Here’s a brief reminder about some fundamental truths of climate science:

1Global temperatures are rising at unprecedented levels

• 2016 was the third consecutive year of record-warm global average temperatures.

• 16 of the 17 warmest years on record have occurred this century.

• Average global temperatures have been above the 20th-century average for the past 40 consecutive years.

• Since 1880, global temperatures have risen by more than 1°C (1.8°F), while levels of carbon dioxide in the atmosphere have increased from 280 parts per million (ppm) to more than 400ppm.

2 Extreme weather events are becoming more frequent and more severe

As the atmosphere and ocean warm, they provide additional energy for extreme weather to tap into. For example, warmer temperatures allow the atmosphere to hold more moisture, which can drive heavier downpours. Melting land-based ice combined with warming oceans fuels global sea level rise, which amplifies storm surge and coastal flooding:

• Coastal flooding from high tides has increased by 364 per cent to 925 per cent in locations on all three US coasts over the last 50 years.

• Heavy precipitation events have increased in every region of the contiguous United States since the late 1950s.

• The record rainfall that devastated Louisiana last August was one of six 1-in-1,000 year rainfall events that occurred in the US last year. The deluge caused $10 billion in damages while inundating the state with more than seven trillion gallons of water (three times as much rain as the state received during Hurricane Katrina). Scientists found it to be 40 per cent more likely to occur today than in 1900 as a result of climate change.

• 15 extreme weather events each costing $1 billion or more occurred in the US in 2016, causing $46 billion in aggregate damages. Even when adjusting for inflation, four of the five years with the most billion-dollar extreme weather events in the US have occurred since 2010.

3Human activity is the main cause of climate change

Scientists have determined that it is extremely likely that the increase in greenhouse gas emissions from human activity has caused more than half of the observed increase in temperature over the last 60 years, making it the largest driver of climate change.

When models only include natural drivers of climate change, such as natural variability and volcanic eruptions, they cannot reproduce the recent increase in temperature. Only when models include the increase in greenhouse gas emissions due to human activities can they replicate the observed changes.

Meanwhile, observations over the last 40 years indicate with high confidence that increased heat in the oceans, as well as glacier loss in areas such as Greenland, account for the overwhelming majority of sea level rise. Indeed, the impact of human-driven warming is widespread — in the ocean, in changes to the global water cycle, in reductions in snow and ice, in sea level rise and in many extreme weather events.

4 Without action, things are poised to worsen

What we have witnessed to date is only a small taste of what is in store if emissions continue unabated. Scientists have found:

• It is virtually certain there will be more frequent hot and fewer cold extremes in temperature over the majority of land areas.

• Heat waves will very likely occur with higher frequency and last longer.

• The western United States, and especially the Southwest, is expected to become drier.

• The ocean is becoming so acidic so quickly, it is unclear whether and how ocean life can adapt.

• Livestock and fish production are expected to decline, as are many crop yields as a result of altered rainfall, extreme weather and increased pests.

— World Resources Institute


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