The climate of Earth has changed over centuries and millennia, but in recent decades, the Earth’s temperature has risen more quickly than at any time in recorded history. Scientists know that climate change is caused by human activities, mostly due to the burning of fossil fuels – oil, coal and gas – which releases heat-trapping greenhouse gases into the atmosphere. These gases are now at record levels in the atmosphere, trapping the Sun’s heat and raising global temperatures.
But scientists also test whether the natural influence of factors like solar cycles, volcanic activity and internal climate variability could plausibly explain the trends in global temperatures they have observed over the past several decades. They find that these factors alone cannot account for the recent rapid increase in global temperatures, and that when human influences are included, their models reproduce this warming.
Climate Change is already causing health problems. As global temperatures rise, the number of hot days grows — which leads to heat stress and heat-related illnesses – especially in vulnerable people (like children and the elderly). Warmer weather increases the spread of disease through mosquitoes, ticks, fleas, and flies that carry diseases such as West Nile virus, dengue fever, and Lyme disease.
Warmer air also reduces oxygen saturation, leading to respiratory and cardiovascular disease. And as air pollution increases, it triggers asthma and exacerbates hay fever and other allergies. In addition, flooding and storm damage can lead to drinking water contamination and to community displacement — which brings with it social unrest, trauma, and the risk of disease transmission.
Many nations have made commitments to reduce their emissions of greenhouse gases, but it will take a major, rapid transformation in all areas of life to limit the impacts of Climate Change. To meet the goal of keeping global warming below 1.5 degrees Celsius, we will need to transform energy and transportation systems, reorient agriculture, reduce waste, and invest in healthy communities.
Developing countries are most at risk from Climate Change, even though they have emitted less than their fair share of historical greenhouse gas emissions. As the climate crisis worsens, they will be forced to cope with increasing heat and drought, floods, erosion, and loss of land – which will threaten the livelihoods of millions of people and increase poverty rates.
This is why it’s critical to support the National Climate Assessment and to fight against false information from fossil fuel industries and others with financial interests in perpetuating a climate crisis.
The science is clear: we must reduce our carbon emissions to the level of what nature has adapted to over hundreds of thousands of years.
The scientific basis for linking the levels of atmospheric carbon dioxide to global temperatures was established in the last century, thanks to Nobel Prize winner Svante Arrhenius and American scientist David Keeling. Since then, extensive research by thousands of scientists around the world has confirmed that our increased use of fossil fuels has triggered the climate changes we are seeing today.