There is a current warming trend. Since the 1950s, the temperature has risen by about 1 °C. To put it in perspective, the rapid change between ice ages and interglacial periods involves a change in temperature of about 8-10 °C in 20 000 years. While it is true that “climate has always changed”, this does not quite appreciate the rapid rate at which the temperature increase. We know that humans have been releasing a huge amount of carbon dioxide over the past decades. This is because the pH in the oceans are becoming more acidic. Had the increase in carbon dioxide primarily come from natural sources, it would have to mostly come from the oceans, since that is the largest reservoir of carbon dioxide and we would expect the ocean pH to go up and not down as we currently observe.
But how do we know all of these things? How do we know there is a current warming trend? How does the greenhouse effect work? How come human emissions of carbon dioxide is relevant when there is so much of it is already in the atmosphere from natural sources? How do we know that the activity of the sun has declined over the past 50 years? How do we know that natural factors cannot by itself explain the observed warming? Why is it a mistake to claim that there has been no warming for the past few decades? How come there is a difference in global warming impact on different polar ice caps? How do you measure sea level rise? What impacts will a few degrees of warming have on the planet? How do we know about the climate of the past?
Climate Change: Evidence and Causes is a short book from 2014 authored by leading climate scientists in a collaboration between The National Academy of Sciences and The Royal Society to provide a brief introduction to climate change and the role of human emissions of greenhouse gases.
It consists of largely two parts a survey of the scientific underpinnings of climate change as well as answers to 20 common questions about climate change. However, the questions are not arbitrary, but rather follow a logical path through the issues that are currently facing humans when it comes to climate. It starts of by asking and answering questions regarding if there is a current warming trend, how scientists know that humans play a considerable role in the current warming, and why this cannot be attributed to the sun.
It then moves on to discuss atmospheric evidence of global warming and the role of carbon dioxide. In particular, it refutes common misunderstandings such as climate always changing, historical levels of carbon dioxide and the alleged global warming pause. It follows up this discussion by the difference between weather and climate as well as the effects of warming on the polar ice caps, frequency and severity of storms, sea level rise, and ocean acidification.
It finishes of my responding to questions about consensus, how bad a few degrees of warming can be, how scientists handle uncertainties, and the potential impact of methane release from the arctic. It is a fantastic resource for anyone who wants to go from knowing very little to having a good grasp of many of the issues. Perfect for sending to friends and family that either deny that global warming is happening or feel anxious about what is happening due to having too little information. It is also excellent to link in debates about global warming online because it contains information in an easily digestible format and a lot of frequently asked questions.
The book can be read online or downloaded in PDF format. You do not need to register an account and can download it as a guest. You have to put in an email address, but it will take any arbitrary address.