(CNN) -- As greenhouse gases cause average temperatures to climb worldwide, human health will suffer, scientists say.
A study in the journal Nature Climate Change suggests that heat deaths in Manhattan will increase over the rest of this century in connection with higher temperatures associated with global warming. In the 2020s, heat-related deaths could rise about 20% compared with the 1980s, according to the research.
"This paper helps to remind people that climate change is real, that it's happening and we need to prepare and make ourselves as resilient as we can to climate change," said Patrick Kinney, the study's senior author and director of the Columbia Climate and Health Program at Columbia University's Mailman School of Public Health. "It's a real problem that we face. It's not insurmountable."
In the 2050s, the study projects, climate change could be associated with a rise of up to 49% in heat-related deaths. And by the 2080s, the average heat-related deaths could go up as much as 91%. For reference, the average number of heat-related deaths in the 1980s was 369.
Although rising temperatures mean fewer cold-related deaths, the magnitude of the heat-related deaths still results in an overall net loss of life when it comes to temperature-related mortality. Projections in this study comparing the two found a net increase in deaths of up to 6.2% in the 2020s, up to 15.4% in the 2050s and up to 31% in the 2080s.
Scientists paired projections of future temperatures, which are expected to rise because of climate change, and plugged them into a function relating this information to risk of death. To come up with that function, they analyzed data on daily temperatures and deaths in Manhattan in the 1980s.
These numbers all relate to a scenario in which greenhouse gases are high by the end of the century, with greenhouse gas emissions continuing to grow. The projected death tolls are slightly more modest in a scenario where social and environmental consciousness work to mitigate emissions, the study says, but even then, heat deaths would be expected to rise about 50% in 2080, as compared with 100 years earlier.
In the 2080s, the months of May and September are projected to have the largest percentage increases in temperature-related deaths.
Kinney's study does have some shortcomings. For example, it did not take into account the expected rise in population of Manhattan in the future, or the effects of hurricanes and other extreme weather events when calculating death tolls.
The study is similar to an analysis done in 2011 about Chicago, led by Francesca Dominici of Harvard School of Public Health. She and colleagues wrote in the journal Environmental Health Perspectives that between 2081 and 2100, Chicago could suffer up to 2,217 excess deaths per year that would be attributable to heat waves, although the lower estimate was 166 such deaths.
The consensus in the scientific community is that human activity - namely burning coal, oil and natural gas - has been the engine behind the rapidly rising carbon dioxide levels in the atmosphere.
Earlier this month, carbon dioxide levels reached a key milestone -- 400 parts per million - at the Mauna Loa Observatory in Hawaii.
With warmer temperatures and melting icecaps, sea levels rise, making any individual storm more disastrous. The sea level near New York City was about 10 inches higher in 2012 than in 1900, which compounded the effects of Superstorm Sandy, said J. Marshall Shepherd, climate change expert and professor at the University of Georgia.
It's impossible to say that any given heat wave or severe storm is "caused by climate change," but changing climate patterns do raise the risk for these events.
Kinney likens this to drunk driving. A sober driver has a risk of getting into an accident to begin with, but after a couple of drinks, that risk goes up. Similarly, as humans pump more greenhouse gas into the atmosphere, the changes of extreme weather events go up.
"Greenhouse gases are kind of like the alcohol in the system of the climate," Kinney said.
New York is already planning strategies to combat heat-related illness from climate change, Kinney said. Planting trees and making "green" roofs, or simply painting black roofs white, can all help cool the city. When high temperatures are on the way, there could be better ways to get the word out to vulnerable populations.
"With careful planning we can protect most people from the effects shown in this paper," Kinney said.