Most comprehensive records show warming leads to irreversible food and water shortages, pandemics, species collapse, and carbon sinks.

2 Grim situation and consensus on human activities changing climate A team consist of 93 scientists has published a exceptionally comprehensive record of paleoclimatic data across the past 12,000 years. It contains 1,319 data records collected from 679 sites around the world and from samples such as marine sediments, lake sediments, peat, coral, cave sediments and glacial ice cores. From this data, the researchers mapped changes in surface air temperatures over the 12,000 years since the last iceage. The figure is compared to the century average temperature between 1800 and 1900 to track changes likely to be brought about by the Industrial Revolution. As expected, temperatures at the start of the period were much cooler than the 19th century baseline. But over the next few thousand years, temperatures rose steadily, eventually surpassing the baseline. Temperatures peaked 6,500 years ago, and since then, the planet has been slowly but surely cooling, seemingly driven by slow cycles in Earth's orbit, which reduced the amount of sunlight in the northern hemisphere's summer and ultimately led to the 'Little Ice Age' of recent centuries. In a relatively short period since the middle of the 19th century, human activity has increased the average temperature by as much as 1℃, a huge peak that is higher than the peak of 6500 years ago (Fig.1) [1].

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Fig. 1. Global mean surface temperature from the Temperature 12k database using different reconstruction methods [1]. A recent report by Xu Chi, a professor at the School of Life Sciences at Nanjing University, showed that, on a global scale, humans have been distributed in more stable climate conditions for the past 6,000 years. The research was conducted using interdisciplinary studies such as ecology, archaeology and climatology. If the global population is to remain in this climatic niche, according to the current trends in climate change, by 2070, some 3 billion people would be living in extreme temperatures similar to those currently found in the heart of the Sahara.

Max Callaghan and other researchers used Bert model machine learning to identify and classify 100,000 climate impact research papers, in an attempt to determine how many people in the world are already experiencing the effects of the climate crisis. They drawed important conclusions: For climate change research, it is more focused on richer countries in Europe and North America, with about twice as many studies as low-income countries such as Africa and the Pacific Islands. The combined results show that the vast majority of the world, with more than 80% of the land area and 85% of the population, is currently experiencing the impacts of the climate crisis (Fig.2) [2].

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Fig. 2. A global density map of climate impact evidence The people of the Republic of Kiribati, an island nation in the central Pacific Ocean, have been forced to move their homes due to rising sea levels. They are at constant risk of flooding and waves. The rich and the rich countries emit more carbon, while the poor don't even own a house or a car. The poor who are most dependent on nature and want to live in harmony bear more of the impacts of climate change. The modern mode of development and industrialization were brought by the people of rich countries. Their technological strength, sustainable development concept, capital and management strength can also bring about visible results in a short period of time. There is no doubt that developed countries need to take the lead in solving the climate problem.

3 IPCC report The effects of human activities on the climate system has been the core content of every assessment report by the United Nations' Intergovernmental Panel on Climate Change (IPCC).The latest sixth IPCC assessment report adopted climate models participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6), so that the impacts of different anthropogenic forcing factors on the climate system can be further recognized and quantified, and the understanding of the effects of human activities on climate change can be deepened. The indicators in different layers of the climate system, including the atmosphere, oceans, cryosphere and the surface of the change of the climate change , can detect the influence of human activity.The sixth time evaluation report suggests extreme cold and extreme warm events change in global and most of the mainland are likely to be the main reason of the greenhouse gases caused by human activities. The intensification of global heavy rainfall in recent decades may also be due to the influence of human activities. The decline in spring snow cover in the Northern Hemisphere since 1950 has also been linked to human activity, which is also likely to be a major driver of the recent universal glacier retreat that has occurred nearly worldwide. Human activity is most likely the main driver of global sea-level rise and ocean heat content increase since the 1970s.On 28 February 2022, the IPCC released its report "Climate Change 2022: Impacts, Adaptation and Vulnerability". The report argues that warming has pushed the majority of the planet's ecosystems to "hard limits of human adaptation" -- the point at which human societies will be unable to adapt to any more change. Antonio Guterres, Secretary-General of the United Nations, said: Today's IPCC report is an 'atlas of human suffering' ", and the climate problem is worse than ever [3]. The latest IPCC report, which is more than 2,000 pages and was compiled by 270 scientists after reviewing numerous independent studies, provides a comprehensive overview of the entire body of scientific research on climate change, with a focus on its effects on ecosystems, wildlife and human societies. According to the IPCC report, some of the consequences we are already seeing at current levels of warming include: 1) The disease is spreading to more areas 2) Species are dying out everywhere 3) Local animal and plant populations die or migrate, irreversibly changing local ecosystems 4) Plants and mammals died in large numbers due to droughts and heat waves 5) Major food systems begin to collapse 6) Past carbon sinks, such as the Amazon rainforest and Arctic permafrost, turn into sources of greenhouse gas emissions 7) As a result of climate change, half of the world's living things are at present moving habitats, destroying ecosystems everywhere. Half the world's population faces water shortages for at least part of the year. The risks to the food system are high: about 8 percent of the world's farmland could become unusable if warming reaches 1.5 degrees.

4 The serious impact of climate change on infectious diseases, etc 4.1 Increase the spread of infectious diseases The Lancet Countdown on Health and Climate Change released its 2020 report, along with the first regional report for the Asian region. An accompanying editorial in The Lancet noted that both the climate crisis and the zoonotic disease COVID-19 are caused by human activities that trigger environmental degradation, and that the impacts of these two crises are also intersecting and superimposed [4]. When these two crisis responses are developed in collaboration, they offer an opportunity of population health improvement, shaping a sustainable future, and better conservation of the earth's remaining natural resources and biodiversity. After the COVID-19 pandemic, governments will begin implementing economic recovery plans, with special attention to climate change and a green recovery. In the latest study, published in the August issue of Nature Climate Change, Camilo Mora et al. systematically screened the literature to link 286 unique human pathogen diseases to 10 climate hazards, such as warming, flooding or drought. Of these, 277 were exacerbated by at least one climate hazard and only nine were weakened by it. Overall, 58% of the reliably documented list of infectious diseases affecting humans have been shown to be exacerbated by climate change [5]. The five-year study of 3,139 mammal species simulated how their movement trajectories would change under a range of global warming scenarios and then analyzed how virus transmission would be affected, according to a study published April 28 in Nature. By 2070, as global warming causes thousands of mammal species to migrate, this will drive thousands of viruses to spread between different mammals. Even at relatively low levels of global warming, projections suggest that at least 15,000 events of crossspecies transmission of one or more viruses will occur within the next 50 years. These viruses pose a huge threat, since humans lack immunity to them due to never being exposed to these viruses [6]. The risk of dengue fever spreading in China has increased over the past three or four decades. Dengue fever is a mosquito-borne disease. Climate change has changed the humidity and temperature of the environment, and improved the transmission environment and survival of mosquitoes. As a result, the risk of transmission of this infectious disease has increased worldwide, and its epidemic range is also spreading to the northern regions, which used to be colder. Climate change increases the risk of foodborne, waterborne and vector-borne diseases. Climate change and its drivers are creating conditions for the spread of infectious diseases as warming expands the distribution of pathogens and their hosts, as precipitation changes accelerate pathogen maturation and vector reproduction. Dengue fever, chikungunya, Zika, malaria and cholera threaten unravel decades of progress that countries have made in controlling diseases like dengue fever, Chikungunya, Zika, malaria and cholera.